From: Leon Romanovsky leonro@nvidia.com

P2PDMA selects a mapping without receiving the Request's ordering or Address Type attributes. Its ACS handles only strictly ordered Requests carrying an Untranslated address.

Document that the result is not defined for Relaxed Ordering or ATS-translated Requests because those TLP attributes can select different routes through the fabric.

Reviewed-by: Logan Gunthorpe logang@deltatee.com Signed-off-by: Leon Romanovsky leonro@nvidia.com --- Documentation/driver-api/pci/p2pdma.rst | 7 +++++++ 1 file changed, 7 insertions(+)

diff --git a/Documentation/driver-api/pci/p2pdma.rst b/Documentation/driver-api/pci/p2pdma.rst index 63cff9e4d2c9..80f8fec9b0e9 100644 --- a/Documentation/driver-api/pci/p2pdma.rst +++ b/Documentation/driver-api/pci/p2pdma.rst @@ -15,6 +15,13 @@ then based on the ACS settings the transaction can route entirely within the PCIe hierarchy and never reach the root port. The kernel will evaluate the PCIe topology and always permit P2P in these well-defined cases.

+This evaluation assumes clients issue strictly ordered Requests carrying an +Untranslated address. Its result is not defined when clients use Relaxed +Ordering or issue ATS-translated Requests because those TLP attributes can +select different routes through the fabric. Unless ACS Translation Blocking +is enabled, a Port with ACS Direct Translated P2P enabled routes a +Translated Request directly to the peer regardless of the redirect controls. + However, if the P2P transaction reaches the host bridge then it might have to hairpin back out the same root port, be routed inside the CPU SOC to another PCIe root port, or routed internally to the SOC.

From: Leon Romanovsky leonro@nvidia.com

pci_acs_flags_enabled() and the Intel SPT PCH quirk use ACS registers without checking config-space read errors. A failed read may leave control state indeterminate yet allow the device to satisfy requested isolation controls.

Return false when either ACS capability or control state cannot be read. An unknown state cannot prove isolation.

Signed-off-by: Leon Romanovsky leonro@nvidia.com --- drivers/pci/pci.c | 3 ++- drivers/pci/quirks.c | 6 ++++-- 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index b2879a6be5f8..f7d94ecf9157 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3594,7 +3594,8 @@ static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags) */ acs_flags &= (pdev->acs_capabilities | PCI_ACS_EC);

- pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl); + if (pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl)) + return false; return (ctrl & acs_flags) == acs_flags; }

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c index de9bbccda21f..d5c3e6802840 100644 --- a/drivers/pci/quirks.c +++ b/drivers/pci/quirks.c @@ -4992,10 +4992,12 @@ static int pci_quirk_intel_spt_pch_acs(struct pci_dev *dev, u16 acs_flags) return -ENOTTY;

/* see pci_acs_flags_enabled() */ - pci_read_config_dword(dev, pos + PCI_ACS_CAP, &cap); + if (pci_read_config_dword(dev, pos + PCI_ACS_CAP, &cap)) + return 0; acs_flags &= (cap | PCI_ACS_EC);

- pci_read_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, &ctrl); + if (pci_read_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, &ctrl)) + return 0;

return pci_acs_ctrl_enabled(acs_flags, ctrl); }

From: Leon Romanovsky leonro@nvidia.com

P2PDMA documentation describes ACS controls as path-wide, although Request and Completion controls apply to different transaction directions and only affect peer-versus-upstream decisions at the path divergence.

Document the fixed client and provider roles, the divergence port checked for each TLP direction, and the conservative handling of unreadable ACS state. Clarify which controls disable_acs_redir changes.

Signed-off-by: Leon Romanovsky leonro@nvidia.com --- Documentation/admin-guide/kernel-parameters.txt | 9 +++++---- Documentation/driver-api/pci/p2pdma.rst | 13 +++++++++++++ 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 68647ff4bdd2..43a25f3f94fd 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5291,10 +5291,11 @@ Kernel parameters disable_acs_redir=<pci_dev>[; ...] Specify one or more PCI devices (in the format specified above) separated by semicolons. - Each device specified will have the PCI ACS - redirect capabilities forced off which will - allow P2P traffic between devices through - bridges without forcing it upstream. Note: + Each device specified will have the PCI ACS P2P + Request Redirect, Completion Redirect, and Egress + Control features forced off. This may allow P2P + traffic through bridges that would otherwise be + redirected upstream. Note: this removes isolation between devices and may put more devices in an IOMMU group. config_acs= diff --git a/Documentation/driver-api/pci/p2pdma.rst b/Documentation/driver-api/pci/p2pdma.rst index 80f8fec9b0e9..42b18610bf7d 100644 --- a/Documentation/driver-api/pci/p2pdma.rst +++ b/Documentation/driver-api/pci/p2pdma.rst @@ -15,6 +15,19 @@ then based on the ACS settings the transaction can route entirely within the PCIe hierarchy and never reach the root port. The kernel will evaluate the PCIe topology and always permit P2P in these well-defined cases.

+The client remains the PCIe requester when it reads or writes provider memory. +Where the paths diverge, the kernel therefore evaluates P2P Request Redirect +and Egress Control on the client-side port, and P2P Completion Redirect on the +provider-side port for completions from a read. An enabled Egress Control is +conservatively treated as a Request redirect. + +Below the divergence, the route toward the other branch is already upstream, +so those P2P redirect controls do not affect it. Redirect controls for the +reverse transaction directions do not affect the mapping. P2P DMA is routed +through the host bridge when either applicable port redirects. If an ACS +Control register cannot be read, P2P DMA is rejected because the kernel cannot +establish a usable route. + This evaluation assumes clients issue strictly ordered Requests carrying an Untranslated address. Its result is not defined when clients use Relaxed Ordering or issue ATS-translated Requests because those TLP attributes can

From: Leon Romanovsky leonro@nvidia.com

calc_map_type_and_dist() returns one mapping type per provider and client, valid only for strictly ordered Requests carrying an Untranslated address. Clients that use Relaxed Ordering or ATS cannot ask what the fabric would do with their traffic.

Add enum pci_p2pdma_tlp_flags to name a class and pci_p2pdma_map_type_tlp() to ask about one. The topology walk and the ACS Control reads do not depend on the class, so decide all of them from the one walk and cache them together, four bits each. Every class still answers alike; the controls that tell them apart come next.

Signed-off-by: Leon Romanovsky leonro@nvidia.com --- drivers/pci/p2pdma.c | 121 +++++++++++++++++++++++++++++++++------------ include/linux/pci-p2pdma.h | 49 ++++++++++++++++-- 2 files changed, 136 insertions(+), 34 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 3a14abf5fe84..fac765d0a16f 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -531,7 +531,7 @@ enum pci_acs_p2pdma_state { * bus addressing be assumed. */ static enum pci_acs_p2pdma_state -pci_acs_p2pdma_request(u16 ctrl) +pci_acs_p2pdma_request(u16 ctrl, unsigned int tlp_flags) { return ctrl & (PCI_ACS_RR | PCI_ACS_EC) ? PCI_ACS_P2PDMA_REDIRECT : PCI_ACS_P2PDMA_DIRECT; @@ -543,7 +543,7 @@ pci_acs_p2pdma_request(u16 ctrl) * affects a Completion. */ static enum pci_acs_p2pdma_state -pci_acs_p2pdma_completion(u16 ctrl) +pci_acs_p2pdma_completion(u16 ctrl, unsigned int tlp_flags) { return ctrl & PCI_ACS_CR ? PCI_ACS_P2PDMA_REDIRECT : PCI_ACS_P2PDMA_DIRECT; @@ -600,13 +600,16 @@ struct pci_p2pdma_acs_path { * the peer's bus addresses. */ static enum pci_p2pdma_map_type -pci_p2pdma_route(const struct pci_p2pdma_acs_path *path) +pci_p2pdma_route(const struct pci_p2pdma_acs_path *path, + unsigned int tlp_flags) { if (path->unreadable) return PCI_P2PDMA_MAP_NOT_SUPPORTED;

- if (pci_acs_p2pdma_request(path->req_ctrl) == PCI_ACS_P2PDMA_DIRECT && - pci_acs_p2pdma_completion(path->cpl_ctrl) == PCI_ACS_P2PDMA_DIRECT) + if (pci_acs_p2pdma_request(path->req_ctrl, tlp_flags) == + PCI_ACS_P2PDMA_DIRECT && + pci_acs_p2pdma_completion(path->cpl_ctrl, tlp_flags) == + PCI_ACS_P2PDMA_DIRECT) return PCI_P2PDMA_MAP_BUS_ADDR;

return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; @@ -620,7 +623,8 @@ static void pci_p2pdma_warn_path(struct pci_dev *client, struct pci_dev *provider, const struct pci_p2pdma_acs_path *path, struct pci_dev *a_child, - struct pci_dev *b_child) + struct pci_dev *b_child, + unsigned int tlp_flags) { struct seq_buf acs_list; char buf[128]; @@ -633,9 +637,11 @@ static void pci_p2pdma_warn_path(struct pci_dev *client, }

seq_buf_init(&acs_list, buf, sizeof(buf)); - if (pci_acs_p2pdma_completion(path->cpl_ctrl) != PCI_ACS_P2PDMA_DIRECT) + if (pci_acs_p2pdma_completion(path->cpl_ctrl, tlp_flags) != + PCI_ACS_P2PDMA_DIRECT) seq_buf_print_bus_devfn(&acs_list, a_child); - if (pci_acs_p2pdma_request(path->req_ctrl) != PCI_ACS_P2PDMA_DIRECT) + if (pci_acs_p2pdma_request(path->req_ctrl, tlp_flags) != + PCI_ACS_P2PDMA_DIRECT) seq_buf_print_bus_devfn(&acs_list, b_child);

/* Drop the final semicolon; the list is not empty here. */ @@ -803,6 +809,31 @@ static unsigned long map_types_idx(struct pci_dev *client) return (pci_domain_nr(client->bus) << 16) | pci_dev_id(client); }

+/* + * One cache entry holds the routing of every TLP class, four bits each, + * indexed by the &enum pci_p2pdma_tlp_flags combination that selects it. An + * absent entry reads back as PCI_P2PDMA_MAP_UNKNOWN in every class. + */ +static_assert(PCI_P2PDMA_MAP_THRU_HOST_BRIDGE < 16); + +static unsigned long +pci_p2pdma_map_types_pack(const enum pci_p2pdma_map_type *type) +{ + unsigned long val = 0; + unsigned int flags; + + for (flags = 0; flags < PCI_P2PDMA_TLP_CLASSES; flags++) + val |= (unsigned long)type[flags] << (flags * 4); + + return val; +} + +static enum pci_p2pdma_map_type +pci_p2pdma_map_types_unpack(unsigned long val, unsigned int tlp_flags) +{ + return (val >> (tlp_flags * 4)) & 0xf; +} + /* * Calculate the P2PDMA mapping type and distance between two PCI devices. * @@ -832,6 +863,10 @@ static unsigned long map_types_idx(struct pci_dev *client) * check Request Redirect and Egress Control on the client-side port, and * Completion Redirect for read Completions on the provider-side port. * + * Those controls apply to different TLPs, so every class named by &enum + * pci_p2pdma_tlp_flags is decided from the one walk and cached together; + * @tlp_flags selects which one is returned. + * * If ACS redirects traffic at either divergence port, return * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE. If the ACS Control register cannot be * read, return PCI_P2PDMA_MAP_NOT_SUPPORTED. Otherwise, return @@ -845,14 +880,16 @@ static unsigned long map_types_idx(struct pci_dev *client) */ static enum pci_p2pdma_map_type calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, - int *dist, bool verbose) + int *dist, unsigned int tlp_flags, bool verbose) { - enum pci_p2pdma_map_type map_type = PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; + enum pci_p2pdma_map_type map_type[PCI_P2PDMA_TLP_CLASSES]; struct pci_dev *a = provider, *b = client, *bb; struct pci_dev *a_child = NULL, *b_child = NULL; struct pci_p2pdma_acs_path path = {}; struct pci_p2pdma *p2pdma; bool cpu_p2pdma, host_whitelisted = false; + bool host_fallback = false; + unsigned int flags; int dist_a = 0; int dist_b = 0;

@@ -886,6 +923,8 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, * request can only get to the peer through the host bridge. */ *dist = dist_a + dist_b; + for (flags = 0; flags < PCI_P2PDMA_TLP_CLASSES; flags++) + map_type[flags] = PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; goto map_through_host_bridge;

check_paths_acs: @@ -905,18 +944,24 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, }

/* - * Below a shared upstream bridge, a path whose divergence ports do not - * redirect routes the request directly. + * The walk and the config reads above serve every class; only the + * decision below depends on the kind of TLP being routed. */ - map_type = pci_p2pdma_route(&path); - if (map_type == PCI_P2PDMA_MAP_BUS_ADDR) - goto done; + for (flags = 0; flags < PCI_P2PDMA_TLP_CLASSES; flags++) { + map_type[flags] = pci_p2pdma_route(&path, flags); + if (map_type[flags] == PCI_P2PDMA_MAP_THRU_HOST_BRIDGE) + host_fallback = true; + }

- if (verbose) - pci_p2pdma_warn_path(client, provider, &path, a_child, b_child); + if (verbose && map_type[0] != PCI_P2PDMA_MAP_BUS_ADDR) + pci_p2pdma_warn_path(client, provider, &path, a_child, + b_child, 0);

- /* An unreadable control does not establish an upstream redirect. */ - if (path.unreadable) + /* + * Nothing needs the host bridge: the classes that did not get a direct + * route have no fallback that would use it. + */ + if (!host_fallback) goto done;

map_through_host_bridge: @@ -929,16 +974,19 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, if (verbose) pci_warn(client, "cannot be used for peer-to-peer DMA as the client and provider (%s) do not share an upstream bridge or whitelisted host bridge\n", pci_name(provider)); - map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; + for (flags = 0; flags < PCI_P2PDMA_TLP_CLASSES; flags++) + if (map_type[flags] == PCI_P2PDMA_MAP_THRU_HOST_BRIDGE) + map_type[flags] = PCI_P2PDMA_MAP_NOT_SUPPORTED; } done: rcu_read_lock(); p2pdma = rcu_dereference(provider->p2pdma); if (p2pdma) xa_store(&p2pdma->map_types, map_types_idx(client), - xa_mk_value(map_type), GFP_ATOMIC); + xa_mk_value(pci_p2pdma_map_types_pack(map_type)), + GFP_ATOMIC); rcu_read_unlock(); - return map_type; + return map_type[tlp_flags]; }

/** @@ -979,7 +1027,7 @@ int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients, return -1; }

- map = calc_map_type_and_dist(provider, pci_client, &distance, + map = calc_map_type_and_dist(provider, pci_client, &distance, 0, verbose);

pci_dev_put(pci_client); @@ -1244,25 +1292,34 @@ void pci_p2pmem_publish(struct pci_dev *pdev, bool publish) EXPORT_SYMBOL_GPL(pci_p2pmem_publish);

/** - * pci_p2pdma_map_type - Determine the mapping type for P2PDMA transfers + * pci_p2pdma_map_type_tlp - Determine the mapping type for P2PDMA transfers * @provider: P2PDMA provider structure * @dev: Client device that initiates the transfer + * @tlp_flags: &enum pci_p2pdma_tlp_flags describing the TLPs @dev will issue * * Determines how peer-to-peer DMA transfers should be mapped between * the provider and the client device. The mapping type indicates whether * the transfer can be done directly through PCI switches or must go * through the host bridge. + * + * ACS routes a peer-to-peer transaction by the attributes its TLPs carry, so + * the answer depends on @tlp_flags. A caller that passes flags its traffic + * does not match gets a mapping the fabric will not deliver. */ -enum pci_p2pdma_map_type pci_p2pdma_map_type(struct p2pdma_provider *provider, - struct device *dev) +enum pci_p2pdma_map_type +pci_p2pdma_map_type_tlp(struct p2pdma_provider *provider, struct device *dev, + unsigned int tlp_flags) { - enum pci_p2pdma_map_type type = PCI_P2PDMA_MAP_NOT_SUPPORTED; struct pci_dev *pdev = to_pci_dev(provider->owner); + unsigned long cache_index, cached = 0; + enum pci_p2pdma_map_type type; struct pci_p2pdma *p2pdma; - unsigned long cache_index; struct pci_dev *client; int dist;

+ if (WARN_ON_ONCE(tlp_flags >= PCI_P2PDMA_TLP_CLASSES)) + return PCI_P2PDMA_MAP_NOT_SUPPORTED; + if (!pdev->p2pdma) return PCI_P2PDMA_MAP_NOT_SUPPORTED;

@@ -1276,12 +1333,14 @@ enum pci_p2pdma_map_type pci_p2pdma_map_type(struct p2pdma_provider *provider, p2pdma = rcu_dereference(pdev->p2pdma);

if (p2pdma) - type = xa_to_value(xa_load(&p2pdma->map_types, - cache_index)); + cached = xa_to_value(xa_load(&p2pdma->map_types, + cache_index)); rcu_read_unlock(); + type = pci_p2pdma_map_types_unpack(cached, tlp_flags);

if (type == PCI_P2PDMA_MAP_UNKNOWN) - return calc_map_type_and_dist(pdev, client, &dist, true); + return calc_map_type_and_dist(pdev, client, &dist, tlp_flags, + true);

return type; } diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h index dd17501ba1b6..36045b1b730c 100644 --- a/include/linux/pci-p2pdma.h +++ b/include/linux/pci-p2pdma.h @@ -28,6 +28,33 @@ struct p2pdma_provider { u64 bus_offset; };

+/** + * enum pci_p2pdma_tlp_flags - Properties of the TLPs a client will issue + * + * These describe the traffic rather than the topology, and select which ACS + * controls apply along the peer-to-peer path. A value of 0 means strictly + * ordered Requests carrying an Untranslated address. + * + * @PCI_P2PDMA_TLP_TRANSLATED: Requests carry an ATS Translated address. PCIe + * r7.0 sec 6.12.3 routes those to the peer regardless of ACS P2P Request + * Redirect and ACS P2P Egress Control wherever ACS Direct Translated P2P + * is enabled. + * @PCI_P2PDMA_TLP_RELAXED_CPL: The provider returns Completions with the + * Relaxed Ordering attribute set. PCIe r7.0 sec 6.12.1.1 never redirects + * those, so ACS P2P Completion Redirect does not gate the path. The + * Completer chooses this attribute and the specification does not require + * it to copy Relaxed Ordering from the Request into the Completion, so a + * caller passing this flag asserts that its provider does. + */ +enum pci_p2pdma_tlp_flags { + PCI_P2PDMA_TLP_TRANSLATED = 1 << 0, + PCI_P2PDMA_TLP_RELAXED_CPL = 1 << 1, +}; + +/* Every combination of the flags above selects one routing class. */ +#define PCI_P2PDMA_TLP_CLASSES \ + ((PCI_P2PDMA_TLP_TRANSLATED | PCI_P2PDMA_TLP_RELAXED_CPL) + 1) + enum pci_p2pdma_map_type { /* * PCI_P2PDMA_MAP_UNKNOWN: Used internally as an initial state before @@ -86,8 +113,9 @@ int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev, bool *use_p2pdma); ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev, bool use_p2pdma); -enum pci_p2pdma_map_type pci_p2pdma_map_type(struct p2pdma_provider *provider, - struct device *dev); +enum pci_p2pdma_map_type +pci_p2pdma_map_type_tlp(struct p2pdma_provider *provider, struct device *dev, + unsigned int tlp_flags); #else /* CONFIG_PCI_P2PDMA */ static inline int pcim_p2pdma_init(struct pci_dev *pdev) { @@ -150,7 +178,8 @@ static inline ssize_t pci_p2pdma_enable_show(char *page, return sprintf(page, "none\n"); } static inline enum pci_p2pdma_map_type -pci_p2pdma_map_type(struct p2pdma_provider *provider, struct device *dev) +pci_p2pdma_map_type_tlp(struct p2pdma_provider *provider, struct device *dev, + unsigned int tlp_flags) { return PCI_P2PDMA_MAP_NOT_SUPPORTED; } @@ -168,6 +197,20 @@ static inline struct pci_dev *pci_p2pmem_find(struct device *client) return pci_p2pmem_find_many(&client, 1); }

+/** + * pci_p2pdma_map_type - Determine the mapping type for P2PDMA transfers + * @provider: P2PDMA provider structure + * @dev: Client device that initiates the transfer + * + * Same as pci_p2pdma_map_type_tlp() for a client issuing strictly ordered + * Requests that carry an Untranslated address. + */ +static inline enum pci_p2pdma_map_type +pci_p2pdma_map_type(struct p2pdma_provider *provider, struct device *dev) +{ + return pci_p2pdma_map_type_tlp(provider, dev, 0); +} + struct pci_p2pdma_map_state { struct p2pdma_provider *mem; enum pci_p2pdma_map_type map;

From: Leon Romanovsky leonro@nvidia.com

ACS redirect controls choose between peer and upstream routes only at the path divergence. Applying them below that point rejects valid nested topologies because traffic already has only an upstream route.

Evaluate Request controls on the client-side divergence port and Completion Redirect on the provider-side port and reject an unreadable ACS Control register.

Fixes: 52916982af48 ("PCI/P2PDMA: Support peer-to-peer memory") Signed-off-by: Leon Romanovsky leonro@nvidia.com --- drivers/pci/p2pdma.c | 101 +++++++++++++++++++++++++++++---------------- include/linux/pci-p2pdma.h | 8 ++-- 2 files changed, 70 insertions(+), 39 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 6da68ec99601..43219a67aaf6 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -516,6 +516,7 @@ static struct pci_dev *find_parent_pci_dev(struct device *dev) }

enum pci_acs_p2pdma_state { + PCI_ACS_P2PDMA_NOT_SUPPORTED, PCI_ACS_P2PDMA_DIRECT, PCI_ACS_P2PDMA_REDIRECT, }; @@ -753,13 +754,13 @@ static unsigned long map_types_idx(struct pci_dev *client) * then to Device B. The mapping type returned depends on the ACS * redirection setting of the ports along the path. * - * The client initiates Requests to provider memory. Check Request Redirect - * on the client path and Completion Redirect for read Completions on the - * provider path. + * The client initiates Requests to provider memory. At the path divergence, + * check Request Redirect and Egress Control on the client-side port, and + * Completion Redirect for read Completions on the provider-side port. * - * If ACS redirect is set on any port in the path, traffic between the - * devices will go through the host bridge, so return - * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; otherwise return + * If ACS redirects traffic at either divergence port, return + * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE. If the ACS Control register cannot be + * read, return PCI_P2PDMA_MAP_NOT_SUPPORTED. Otherwise, return * PCI_P2PDMA_MAP_BUS_ADDR. * * Any two devices that have a data path that goes through the host bridge @@ -773,10 +774,13 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, int *dist, bool verbose) { enum pci_p2pdma_map_type map_type = PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; + enum pci_acs_p2pdma_state state = PCI_ACS_P2PDMA_NOT_SUPPORTED; struct pci_dev *a = provider, *b = client, *bb; + struct pci_dev *a_child = NULL, *b_child = NULL; + struct pci_dev *acs_unreadable = NULL; struct pci_p2pdma *p2pdma; struct seq_buf acs_list; - int acs_cnt = 0; + int acs_redirect_cnt = 0; int dist_a = 0; int dist_b = 0; char buf[128]; @@ -791,51 +795,67 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, */ while (a) { dist_b = 0; - - if (!pci_acs_p2pdma_ctrl(a, &ctrl) || - pci_acs_p2pdma_completion(ctrl) == - PCI_ACS_P2PDMA_REDIRECT) { - seq_buf_print_bus_devfn(&acs_list, a); - acs_cnt++; - } - + b_child = NULL; bb = b;

while (bb) { if (a == bb) - goto check_b_path_acs; + goto check_paths_acs;

+ b_child = bb; bb = pci_upstream_bridge(bb); dist_b++; }

+ a_child = a; a = pci_upstream_bridge(a); dist_a++; }

+ /* + * The paths share no upstream bridge, so there is no direct path for + * ACS to gate: PCI_P2PDMA_MAP_BUS_ADDR is not reachable here and the + * request can only get to the peer through the host bridge. + */ *dist = dist_a + dist_b; goto map_through_host_bridge;

-check_b_path_acs: - bb = b; - - while (bb) { - if (a == bb) - break; +check_paths_acs: + *dist = dist_a + dist_b;

- if (!pci_acs_p2pdma_ctrl(bb, &ctrl) || - pci_acs_p2pdma_request(ctrl) == - PCI_ACS_P2PDMA_REDIRECT) { - seq_buf_print_bus_devfn(&acs_list, bb); - acs_cnt++; + /* + * ACS P2P routing controls apply where a TLP can route toward the peer + * or upstream. Below that divergence, its only route toward the other + * branch is upstream, so redirect controls do not affect the path. + */ + if (a_child && b_child) { + if (pci_acs_p2pdma_ctrl(a_child, &ctrl)) + state = pci_acs_p2pdma_completion(ctrl); + if (state != PCI_ACS_P2PDMA_DIRECT) { + seq_buf_print_bus_devfn(&acs_list, a_child); + if (state == PCI_ACS_P2PDMA_REDIRECT) + acs_redirect_cnt++; + else if (!acs_unreadable) + acs_unreadable = a_child; }

- bb = pci_upstream_bridge(bb); + state = PCI_ACS_P2PDMA_NOT_SUPPORTED; + if (pci_acs_p2pdma_ctrl(b_child, &ctrl)) + state = pci_acs_p2pdma_request(ctrl); + if (state != PCI_ACS_P2PDMA_DIRECT) { + seq_buf_print_bus_devfn(&acs_list, b_child); + if (state == PCI_ACS_P2PDMA_REDIRECT) + acs_redirect_cnt++; + else if (!acs_unreadable) + acs_unreadable = b_child; + } }

- *dist = dist_a + dist_b; - - if (!acs_cnt) { + /* + * Below a shared upstream bridge, a path whose divergence ports do not + * redirect routes the request directly. + */ + if (!acs_unreadable && !acs_redirect_cnt) { map_type = PCI_P2PDMA_MAP_BUS_ADDR; goto done; } @@ -844,10 +864,21 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, /* Drop the final semicolon; the list is not empty here. */ if (!seq_buf_has_overflowed(&acs_list)) acs_list.buffer[acs_list.len - 1] = '\0'; - pci_warn(client, "ACS redirect is set between the client and provider (%s)\n", - pci_name(provider)); - pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n", - seq_buf_str(&acs_list)); + if (acs_unreadable) + pci_warn(client, "ACS Control is unreadable for provider %s at %s\n", + pci_name(provider), pci_name(acs_unreadable)); + else { + pci_warn(client, "ACS redirect is set between the client and provider (%s)\n", + pci_name(provider)); + pci_warn(client, "to disable ACS controls for this path, add the kernel parameter: pci=disable_acs_redir=%s\n", + seq_buf_str(&acs_list)); + } + } + + /* An unreadable control does not establish an upstream redirect. */ + if (acs_unreadable) { + map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; + goto done; }

map_through_host_bridge: diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h index 873de20a2247..dd17501ba1b6 100644 --- a/include/linux/pci-p2pdma.h +++ b/include/linux/pci-p2pdma.h @@ -42,10 +42,10 @@ enum pci_p2pdma_map_type { PCI_P2PDMA_MAP_NONE,

/* - * PCI_P2PDMA_MAP_NOT_SUPPORTED: Indicates the transaction will - * traverse the host bridge and the host bridge is not in the - * allowlist. DMA Mapping routines should return an error when - * this is returned. + * PCI_P2PDMA_MAP_NOT_SUPPORTED: Indicates no safe mapping is available, + * for example because ACS blocks the direct path or the required host + * bridge is not in the allowlist. DMA Mapping routines should return an + * error when this is returned. */ PCI_P2PDMA_MAP_NOT_SUPPORTED,

From: Leon Romanovsky leonro@nvidia.com

Direct Translated P2P does not weaken IOMMU isolation because a Translated Request carries an address supplied by the IOMMU. Config-space read failures, however, leave ACS state unknown and must not report isolation.

Exercise both cases with fake config-space operations. Also cover missing and unrequested controls and a missing ACS capability.

Signed-off-by: Leon Romanovsky leonro@nvidia.com --- drivers/pci/pci.c | 4 +- drivers/pci/pci.h | 1 + drivers/pci/pci_acs_test.c | 138 +++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 142 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index f7d94ecf9157..4a9ab3882aac 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3578,7 +3578,8 @@ void pci_configure_ari(struct pci_dev *dev) } }

-static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags) +VISIBLE_IF_KUNIT +bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags) { int pos; u16 ctrl; @@ -3598,6 +3599,7 @@ static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags) return false; return (ctrl & acs_flags) == acs_flags; } +EXPORT_SYMBOL_IF_KUNIT(pci_acs_flags_enabled);

/** * pci_acs_enabled - test ACS against required flags for a given device diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 56f821e40637..5bc703ff0c86 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -1104,6 +1104,7 @@ enum pci_acs_p2pdma_state { };

#if IS_ENABLED(CONFIG_KUNIT) +bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags); enum pci_acs_p2pdma_state pci_acs_p2pdma_request(u16 ctrl, unsigned int tlp_flags); enum pci_acs_p2pdma_state pci_acs_p2pdma_completion(u16 ctrl, diff --git a/drivers/pci/pci_acs_test.c b/drivers/pci/pci_acs_test.c index 28eced6dd672..880fc810080a 100644 --- a/drivers/pci/pci_acs_test.c +++ b/drivers/pci/pci_acs_test.c @@ -102,6 +102,140 @@ static void pci_acs_p2pdma_completion_test(struct kunit *test) c->expect); }

+/* Flags an IOMMU asks for; see REQ_ACS_FLAGS in drivers/iommu/iommu.c. */ +#define ACS_REQ_FLAGS (PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF) +#define ACS_ALL_CAPS (PCI_ACS_SV | PCI_ACS_TB | PCI_ACS_RR | PCI_ACS_CR | \ + PCI_ACS_UF | PCI_ACS_DT) +#define ACS_TEST_CAP 0x100 + +struct acs_ctrl_cfg { + unsigned int devfn; + u16 cap; /* Offset where the ACS capability responds */ + u16 ctrl; + bool fail_read; +}; + +static int acs_ctrl_read(struct pci_bus *bus, unsigned int devfn, + int where, int size, u32 *val) +{ + struct acs_ctrl_cfg *cfg = bus->sysdata; + + *val = 0; + if (cfg->fail_read) + return PCIBIOS_DEVICE_NOT_FOUND; + + if (devfn == cfg->devfn && size == 2 && + where == cfg->cap + PCI_ACS_CTRL) + *val = cfg->ctrl; + return PCIBIOS_SUCCESSFUL; +} + +static int acs_ctrl_write(struct pci_bus *bus, unsigned int devfn, + int where, int size, u32 val) +{ + return PCIBIOS_SUCCESSFUL; +} + +static struct pci_ops acs_ctrl_ops = { + .read = acs_ctrl_read, + .write = acs_ctrl_write, +}; + +struct acs_isolation_case { + const char *desc; + u16 ctrl; + u16 req; + bool expect; +}; + +static const struct acs_isolation_case acs_isolation_cases[] = { + { "all_enabled", ACS_REQ_FLAGS, ACS_REQ_FLAGS, true }, + /* Translated Requests remain isolated by their IOMMU translation. */ + { "dt", ACS_REQ_FLAGS | PCI_ACS_DT, ACS_REQ_FLAGS, true }, + { "rr_not_enabled", PCI_ACS_SV | PCI_ACS_CR | PCI_ACS_UF, + ACS_REQ_FLAGS, false }, + { "rr_not_required", PCI_ACS_SV | PCI_ACS_CR | PCI_ACS_UF, + PCI_ACS_SV | PCI_ACS_CR | PCI_ACS_UF, true }, +}; + +static void acs_isolation_desc(const struct acs_isolation_case *c, char *desc) +{ + strscpy(desc, c->desc, KUNIT_PARAM_DESC_SIZE); +} + +KUNIT_ARRAY_PARAM(acs_isolation, acs_isolation_cases, acs_isolation_desc); + +static void pci_acs_flags_enabled_test(struct kunit *test) +{ + const struct acs_isolation_case *c = test->param_value; + struct acs_ctrl_cfg cfg = { + .devfn = PCI_DEVFN(0, 0), + .cap = ACS_TEST_CAP, + .ctrl = c->ctrl, + }; + struct pci_bus *bus = kunit_kzalloc(test, sizeof(*bus), GFP_KERNEL); + struct pci_dev *pdev = kunit_kzalloc(test, sizeof(*pdev), GFP_KERNEL); + + KUNIT_ASSERT_NOT_NULL(test, bus); + KUNIT_ASSERT_NOT_NULL(test, pdev); + + bus->ops = &acs_ctrl_ops; + bus->sysdata = &cfg; + + pdev->bus = bus; + pdev->devfn = cfg.devfn; + pdev->acs_cap = ACS_TEST_CAP; + pdev->acs_capabilities = ACS_ALL_CAPS; + + KUNIT_EXPECT_EQ(test, pci_acs_flags_enabled(pdev, c->req), c->expect); +} + +static bool acs_isolated(struct kunit *test, struct acs_ctrl_cfg *cfg, + u16 acs_cap, u16 acs_flags) +{ + struct pci_bus *bus = kunit_kzalloc(test, sizeof(*bus), GFP_KERNEL); + struct pci_dev *pdev = kunit_kzalloc(test, sizeof(*pdev), GFP_KERNEL); + + KUNIT_ASSERT_NOT_NULL(test, bus); + KUNIT_ASSERT_NOT_NULL(test, pdev); + + bus->ops = &acs_ctrl_ops; + bus->sysdata = cfg; + + pdev->bus = bus; + pdev->devfn = cfg->devfn; + pdev->acs_cap = acs_cap; + pdev->acs_capabilities = ACS_ALL_CAPS; + + return pci_acs_flags_enabled(pdev, acs_flags); +} + +static void pci_acs_flags_no_cap_test(struct kunit *test) +{ + struct acs_ctrl_cfg cfg = { + .devfn = PCI_DEVFN(0, 0), + .cap = 0, + .ctrl = ACS_REQ_FLAGS, + }; + + KUNIT_EXPECT_FALSE(test, acs_isolated(test, &cfg, 0, ACS_REQ_FLAGS)); +} + +static void pci_acs_flags_read_fails_test(struct kunit *test) +{ + u16 no_rr = ACS_REQ_FLAGS & ~PCI_ACS_RR; + struct acs_ctrl_cfg cfg = { + .devfn = PCI_DEVFN(0, 0), + .cap = ACS_TEST_CAP, + .ctrl = ACS_REQ_FLAGS, + }; + + KUNIT_EXPECT_TRUE(test, acs_isolated(test, &cfg, ACS_TEST_CAP, no_rr)); + + cfg.fail_read = true; + KUNIT_EXPECT_FALSE(test, acs_isolated(test, &cfg, ACS_TEST_CAP, no_rr)); +} + /* * Drive calc_map_type_and_dist() over a fabricated PCIe fabric matching the * canonical topology of two devices below one switch: @@ -445,6 +579,10 @@ static struct kunit_case pci_acs_test_cases[] = { acs_request_gen_params), KUNIT_CASE_PARAM(pci_acs_p2pdma_completion_test, acs_completion_gen_params), + KUNIT_CASE_PARAM(pci_acs_flags_enabled_test, + acs_isolation_gen_params), + KUNIT_CASE(pci_acs_flags_no_cap_test), + KUNIT_CASE(pci_acs_flags_read_fails_test), KUNIT_CASE(acs_walk_bus_addr_test), KUNIT_CASE(acs_walk_request_redirect_test), KUNIT_CASE(acs_walk_completion_redirect_test),

From: Leon Romanovsky leonro@nvidia.com

pci_acs_p2pdma_request() and pci_acs_p2pdma_completion() turn an ACS Control register and a TLP class into a routing decision. Which bits apply to which direction and which class is easy to get wrong, and hardware that exposes a given combination may not be at hand.

Drive both from a table of register values and classes, covering the redirect controls per direction and Translation Blocking, Direct Translated P2P and Relaxed Ordering. Direct Translated P2P gets a case with and without a redirect to override, since it changes nothing without one. Exposing the two helpers moves their state enum into pci.h.

Signed-off-by: Leon Romanovsky leonro@nvidia.com --- drivers/pci/Kconfig | 15 ++++++ drivers/pci/Makefile | 1 + drivers/pci/p2pdma.c | 13 ++--- drivers/pci/pci.h | 16 ++++++ drivers/pci/pci_acs_test.c | 121 +++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 157 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig index 0c7408509ba2..7a3eb5beb328 100644 --- a/drivers/pci/Kconfig +++ b/drivers/pci/Kconfig @@ -226,6 +226,21 @@ config PCI_P2PDMA

If unsure, say N.

+config PCI_ACS_KUNIT_TEST + tristate "KUnit tests for PCI ACS P2P routing" if !KUNIT_ALL_TESTS + depends on PCI_P2PDMA && KUNIT + default KUNIT_ALL_TESTS + help + Enable KUnit tests for the PCI ACS peer-to-peer routing decision + logic, including direction-specific Request and Completion + controls that cannot all be exercised on typical peer-to-peer + hardware. + + For more information on KUnit and unit tests in general, refer to + the KUnit documentation in Documentation/dev-tools/kunit/. + + If unsure, say N. + config PCI_LABEL def_bool y if (DMI || ACPI) select NLS diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile index 41ebc3b9a518..6305d128d3df 100644 --- a/drivers/pci/Makefile +++ b/drivers/pci/Makefile @@ -31,6 +31,7 @@ obj-$(CONFIG_PCI_STUB) += pci-stub.o obj-$(CONFIG_PCI_PF_STUB) += pci-pf-stub.o obj-$(CONFIG_PCI_ECAM) += ecam.o obj-$(CONFIG_PCI_P2PDMA) += p2pdma.o +obj-$(CONFIG_PCI_ACS_KUNIT_TEST) += pci_acs_test.o obj-$(CONFIG_XEN_PCIDEV_FRONTEND) += xen-pcifront.o obj-$(CONFIG_VGA_ARB) += vgaarb.o obj-$(CONFIG_PCI_DOE) += doe.o diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 60bd9ec5f993..955e3b41ec1f 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -515,13 +515,6 @@ static struct pci_dev *find_parent_pci_dev(struct device *dev) return NULL; }

-enum pci_acs_p2pdma_state { - PCI_ACS_P2PDMA_NOT_SUPPORTED, - PCI_ACS_P2PDMA_DIRECT, - PCI_ACS_P2PDMA_REDIRECT, - PCI_ACS_P2PDMA_BLOCKED, -}; - /* * Decide how a peer-to-peer Request at an ACS-capable ingress port routes, * from that port's ACS Control register and the Request's Address Type. @@ -531,7 +524,7 @@ enum pci_acs_p2pdma_state { * selects are a direct route and an ACS Violation, and neither one lets peer * bus addressing be assumed. */ -static enum pci_acs_p2pdma_state +VISIBLE_IF_KUNIT enum pci_acs_p2pdma_state pci_acs_p2pdma_request(u16 ctrl, unsigned int tlp_flags) { if (tlp_flags & PCI_P2PDMA_TLP_TRANSLATED) { @@ -558,6 +551,7 @@ pci_acs_p2pdma_request(u16 ctrl, unsigned int tlp_flags) return ctrl & (PCI_ACS_RR | PCI_ACS_EC) ? PCI_ACS_P2PDMA_REDIRECT : PCI_ACS_P2PDMA_DIRECT; } +EXPORT_SYMBOL_IF_KUNIT(pci_acs_p2pdma_request);

/* * Decide how a peer-to-peer Completion at an ACS-capable ingress port routes. @@ -565,7 +559,7 @@ pci_acs_p2pdma_request(u16 ctrl, unsigned int tlp_flags) * affects a Completion, and that one leaves Completions carrying the Relaxed * Ordering attribute alone. */ -static enum pci_acs_p2pdma_state +VISIBLE_IF_KUNIT enum pci_acs_p2pdma_state pci_acs_p2pdma_completion(u16 ctrl, unsigned int tlp_flags) { if (tlp_flags & PCI_P2PDMA_TLP_RELAXED_CPL) @@ -574,6 +568,7 @@ pci_acs_p2pdma_completion(u16 ctrl, unsigned int tlp_flags) return ctrl & PCI_ACS_CR ? PCI_ACS_P2PDMA_REDIRECT : PCI_ACS_P2PDMA_DIRECT; } +EXPORT_SYMBOL_IF_KUNIT(pci_acs_p2pdma_completion);

static const char *pci_acs_p2pdma_state_name(enum pci_acs_p2pdma_state state) { diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index ba3c3fddddc2..c0d2711d73f9 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -2,6 +2,7 @@ #ifndef DRIVERS_PCI_H #define DRIVERS_PCI_H

+#include <kunit/visibility.h> #include <linux/bug.h> #include <linux/align.h> #include <linux/bitfield.h> @@ -1093,6 +1094,21 @@ resource_size_t pci_min_window_alignment(struct pci_bus *bus,

void pci_acs_init(struct pci_dev *dev); void pci_enable_acs(struct pci_dev *dev); + +enum pci_acs_p2pdma_state { + PCI_ACS_P2PDMA_NOT_SUPPORTED, + PCI_ACS_P2PDMA_DIRECT, + PCI_ACS_P2PDMA_REDIRECT, + PCI_ACS_P2PDMA_BLOCKED, +}; + +#if IS_ENABLED(CONFIG_KUNIT) +enum pci_acs_p2pdma_state pci_acs_p2pdma_request(u16 ctrl, + unsigned int tlp_flags); +enum pci_acs_p2pdma_state pci_acs_p2pdma_completion(u16 ctrl, + unsigned int tlp_flags); +#endif + #ifdef CONFIG_PCI_QUIRKS int pci_dev_specific_acs_enabled(struct pci_dev *dev, u16 acs_flags); int pci_dev_specific_enable_acs(struct pci_dev *dev); diff --git a/drivers/pci/pci_acs_test.c b/drivers/pci/pci_acs_test.c new file mode 100644 index 000000000000..ce6b9375da36 --- /dev/null +++ b/drivers/pci/pci_acs_test.c @@ -0,0 +1,121 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * KUnit tests for PCI ACS peer-to-peer routing decisions. + * + * These exercise Request and Completion routing independently of the ACS + * settings exposed by available PCIe hardware. + */ +#include <kunit/test.h> + +#include <linux/pci.h> +#include <linux/pci-p2pdma.h> +#include <linux/pci_regs.h> + +#include "pci.h" + +struct acs_decision_case { + const char *desc; + u16 ctrl; + unsigned int tlp_flags; + enum pci_acs_p2pdma_state expect; +}; + +/* Shorthands to keep the tables below readable. */ +#define ACS_DIRECT PCI_ACS_P2PDMA_DIRECT +#define ACS_REDIR PCI_ACS_P2PDMA_REDIRECT +#define ACS_RO PCI_P2PDMA_TLP_RELAXED_CPL +#define ACS_AT PCI_P2PDMA_TLP_TRANSLATED +#define ACS_BLOCK PCI_ACS_P2PDMA_BLOCKED + +/* Request routing ignores Completion Redirect. */ +static const struct acs_decision_case acs_request_cases[] = { + { "req/none", 0, 0, ACS_DIRECT }, + { "req/rr", PCI_ACS_RR, 0, ACS_REDIR }, + { "req/cr", PCI_ACS_CR, 0, ACS_DIRECT }, + { "req/rr_cr", PCI_ACS_RR | PCI_ACS_CR, 0, ACS_REDIR }, + { "req/ec", PCI_ACS_EC, 0, ACS_REDIR }, + { "req/ec_cr", PCI_ACS_EC | PCI_ACS_CR, 0, ACS_REDIR }, + + /* + * Direct Translated P2P overrides the redirect controls, but only for + * a Request that actually carries a Translated address. + */ + { "req/dt", PCI_ACS_DT, 0, ACS_DIRECT }, + { "req/dt_rr", PCI_ACS_DT | PCI_ACS_RR, 0, ACS_REDIR }, + { "req/at", 0, ACS_AT, ACS_DIRECT }, + { "req/at_rr", PCI_ACS_RR, ACS_AT, ACS_REDIR }, + { "req/at_dt_rr", PCI_ACS_DT | PCI_ACS_RR, ACS_AT, ACS_DIRECT }, + { "req/at_dt_ec", PCI_ACS_DT | PCI_ACS_EC, ACS_AT, ACS_DIRECT }, + + /* + * Translation Blocking rejects a Translated address outright, and + * makes the port ignore Direct Translated P2P. + */ + { "req/tb", PCI_ACS_TB, 0, ACS_DIRECT }, + { "req/tb_rr", PCI_ACS_TB | PCI_ACS_RR, 0, ACS_REDIR }, + { "req/at_tb", PCI_ACS_TB, ACS_AT, ACS_BLOCK }, + { "req/at_tb_dt", PCI_ACS_TB | PCI_ACS_DT, ACS_AT, ACS_BLOCK }, +}; + +/* Completion routing depends only on Completion Redirect. */ +static const struct acs_decision_case acs_completion_cases[] = { + { "cpl/none", 0, 0, ACS_DIRECT }, + { "cpl/rr", PCI_ACS_RR, 0, ACS_DIRECT }, + { "cpl/cr", PCI_ACS_CR, 0, ACS_REDIR }, + { "cpl/rr_cr", PCI_ACS_RR | PCI_ACS_CR, 0, ACS_REDIR }, + { "cpl/ec", PCI_ACS_EC, 0, ACS_DIRECT }, + { "cpl/ec_cr", PCI_ACS_EC | PCI_ACS_CR, 0, ACS_REDIR }, + + /* Relaxed Ordering Completions are never redirected. */ + { "cpl/ro", 0, ACS_RO, ACS_DIRECT }, + { "cpl/ro_cr", PCI_ACS_CR, ACS_RO, ACS_DIRECT }, + { "cpl/ro_rr_cr", PCI_ACS_RR | PCI_ACS_CR, ACS_RO, ACS_DIRECT }, +}; + +#undef ACS_DIRECT +#undef ACS_REDIR +#undef ACS_RO +#undef ACS_AT +#undef ACS_BLOCK + +static void acs_decision_desc(const struct acs_decision_case *c, char *desc) +{ + strscpy(desc, c->desc, KUNIT_PARAM_DESC_SIZE); +} + +KUNIT_ARRAY_PARAM(acs_request, acs_request_cases, acs_decision_desc); +KUNIT_ARRAY_PARAM(acs_completion, acs_completion_cases, acs_decision_desc); + +static void pci_acs_p2pdma_request_test(struct kunit *test) +{ + const struct acs_decision_case *c = test->param_value; + + KUNIT_EXPECT_EQ(test, pci_acs_p2pdma_request(c->ctrl, c->tlp_flags), + c->expect); +} + +static void pci_acs_p2pdma_completion_test(struct kunit *test) +{ + const struct acs_decision_case *c = test->param_value; + + KUNIT_EXPECT_EQ(test, pci_acs_p2pdma_completion(c->ctrl, c->tlp_flags), + c->expect); +} + +static struct kunit_case pci_acs_test_cases[] = { + KUNIT_CASE_PARAM(pci_acs_p2pdma_request_test, + acs_request_gen_params), + KUNIT_CASE_PARAM(pci_acs_p2pdma_completion_test, + acs_completion_gen_params), + {} +}; + +static struct kunit_suite pci_acs_test_suite = { + .name = "pci_acs", + .test_cases = pci_acs_test_cases, +}; +kunit_test_suite(pci_acs_test_suite); + +MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("KUnit tests for PCI ACS peer-to-peer routing decisions");

From: Leon Romanovsky leonro@nvidia.com

A Downstream Port with ACS Translation Blocking enabled treats every Upstream Memory Request whose Address Type is not Untranslated as an ACS Violation, ahead of "any applicable ACS P2P control mechanisms" per PCIe r7.0 sec 6.12.1.1. P2PDMA never looks at that bit, so it reports a bus-addressable path where an ATS client's Requests would be rejected.

Add PCI_ACS_P2PDMA_BLOCKED, and because blocking is not a routing control, scan the whole client-side path for it rather than the divergence port alone. A blocked Request has no host bridge fallback, since the Address Type is rejected wherever the Request is addressed.

Signed-off-by: Leon Romanovsky leonro@nvidia.com --- drivers/pci/p2pdma.c | 105 ++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 96 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 327b6a14e07d..94c0760f27e5 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -519,11 +519,12 @@ enum pci_acs_p2pdma_state { PCI_ACS_P2PDMA_NOT_SUPPORTED, PCI_ACS_P2PDMA_DIRECT, PCI_ACS_P2PDMA_REDIRECT, + PCI_ACS_P2PDMA_BLOCKED, };

/* * Decide how a peer-to-peer Request at an ACS-capable ingress port routes, - * from that port's ACS Control register. + * from that port's ACS Control register and the Request's Address Type. * * Linux does not read the Egress Control Vector, so Egress Control is treated * conservatively as a redirect. Per PCIe r7.0 Table 6-11 the outcomes it @@ -533,6 +534,18 @@ enum pci_acs_p2pdma_state { static enum pci_acs_p2pdma_state pci_acs_p2pdma_request(u16 ctrl, unsigned int tlp_flags) { + if (tlp_flags & PCI_P2PDMA_TLP_TRANSLATED) { + /* + * PCIe r7.0 sec 6.12.1.1: Translation Blocking makes every + * Upstream Memory Request whose Address Type is not + * Untranslated an ACS Violation, taking precedence over the + * P2P controls. Sec 7.7.12.5: Direct Translated P2P "is + * ignored if ACS Translation Blocking Enable is 1b". + */ + if (ctrl & PCI_ACS_TB) + return PCI_ACS_P2PDMA_BLOCKED; + } + return ctrl & (PCI_ACS_RR | PCI_ACS_EC) ? PCI_ACS_P2PDMA_REDIRECT : PCI_ACS_P2PDMA_DIRECT; } @@ -572,6 +585,35 @@ static bool pci_acs_p2pdma_ctrl(struct pci_dev *pdev, u16 *ctrl) return !pci_read_config_word(pdev, pos + PCI_ACS_CTRL, ctrl); }

+/* + * Report whether any port between @client and @divergence rejects Translated + * addresses. @common bounds the walk; @divergence itself is read along with + * the routing controls. A port whose ACS Control cannot be read counts as + * blocking, which withdraws only the Translated classes because an + * Untranslated Request is routed at the divergence. + */ +static bool pci_p2pdma_path_blocks_translation(struct pci_dev *client, + struct pci_dev *divergence, + struct pci_dev *common) +{ + struct pci_dev *pdev; + u16 ctrl; + + for (pdev = pci_upstream_bridge(client); pdev && pdev != common; + pdev = pci_upstream_bridge(pdev)) { + if (pdev == divergence) + continue; + + if (!pci_acs_p2pdma_ctrl(pdev, &ctrl)) + return true; + + if (ctrl & PCI_ACS_TB) + return true; + } + + return false; +} + static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev) { if (!buf) @@ -590,14 +632,35 @@ static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev) * than upstream, so it is where the Request controls apply. * @cpl_ctrl: ACS Control of the provider-side divergence port, likewise for * the Completions travelling back. + * @tb_below: A port between the client and the divergence blocks Translated + * addresses. * @unreadable: First port whose ACS Control could not be read, if any. */ struct pci_p2pdma_acs_path { u16 req_ctrl; u16 cpl_ctrl; + bool tb_below; struct pci_dev *unreadable; };

+/* + * ACS Translation Blocking is not a routing control, so unlike the redirect + * controls it is not decided at the divergence alone. PCIe r7.0 sec 6.12.1.1 + * has every Downstream Port check the Address Type of each Upstream Memory + * Request it receives, ahead of "any applicable ACS P2P control mechanisms". + * A port below the divergence cannot redirect the Request anywhere it was not + * already going, but it can still reject a Translated address. + */ +static enum pci_acs_p2pdma_state +pci_p2pdma_request_state(const struct pci_p2pdma_acs_path *path, + unsigned int tlp_flags) +{ + if (tlp_flags & PCI_P2PDMA_TLP_TRANSLATED && path->tb_below) + return PCI_ACS_P2PDMA_BLOCKED; + + return pci_acs_p2pdma_request(path->req_ctrl, tlp_flags); +} + /* * Combine both directions into a mapping type. Only a path that routes the * Request and the Completions it generates directly can be programmed with @@ -607,11 +670,23 @@ static enum pci_p2pdma_map_type pci_p2pdma_route(const struct pci_p2pdma_acs_path *path, unsigned int tlp_flags) { + enum pci_acs_p2pdma_state req; + if (path->unreadable) return PCI_P2PDMA_MAP_NOT_SUPPORTED;

- if (pci_acs_p2pdma_request(path->req_ctrl, tlp_flags) == - PCI_ACS_P2PDMA_DIRECT && + req = pci_p2pdma_request_state(path, tlp_flags); + + /* + * Translation Blocking rejects the Address Type rather than the + * target, so a blocked Request stays blocked however it is addressed. + * No host bridge fallback keeps a Translated address working; the + * caller has to issue a different kind of Request instead. + */ + if (req == PCI_ACS_P2PDMA_BLOCKED) + return PCI_P2PDMA_MAP_NOT_SUPPORTED; + + if (req == PCI_ACS_P2PDMA_DIRECT && pci_acs_p2pdma_completion(path->cpl_ctrl, tlp_flags) == PCI_ACS_P2PDMA_DIRECT) return PCI_P2PDMA_MAP_BUS_ADDR; @@ -640,12 +715,19 @@ static void pci_p2pdma_warn_path(struct pci_dev *client, return; }

+ if (pci_p2pdma_request_state(path, tlp_flags) == + PCI_ACS_P2PDMA_BLOCKED) { + pci_warn(client, + "ACS Translation Blocking rejects Translated Requests to provider %s\n", + pci_name(provider)); + return; + } + seq_buf_init(&acs_list, buf, sizeof(buf)); if (pci_acs_p2pdma_completion(path->cpl_ctrl, tlp_flags) != PCI_ACS_P2PDMA_DIRECT) seq_buf_print_bus_devfn(&acs_list, a_child); - if (pci_acs_p2pdma_request(path->req_ctrl, tlp_flags) != - PCI_ACS_P2PDMA_DIRECT) + if (pci_p2pdma_request_state(path, tlp_flags) != PCI_ACS_P2PDMA_DIRECT) seq_buf_print_bus_devfn(&acs_list, b_child);

/* Drop the final semicolon; the list is not empty here. */ @@ -864,8 +946,11 @@ pci_p2pdma_map_types_unpack(unsigned long val, unsigned int tlp_flags) * redirection setting of the ports along the path. * * The client initiates Requests to provider memory. At the path divergence, - * check Request Redirect and Egress Control on the client-side port, and - * Completion Redirect for read Completions on the provider-side port. + * check Request Redirect, Egress Control, Translation Blocking and Direct + * Translated P2P on the client-side port, and Completion Redirect for read + * Completions on the provider-side port. Translation Blocking is checked on + * every client-side port instead, because it rejects a Request rather than + * routing it. * * Those controls apply to different TLPs, so every class named by &enum * pci_p2pdma_tlp_flags is decided from the one walk and cached together; @@ -873,8 +958,8 @@ pci_p2pdma_map_types_unpack(unsigned long val, unsigned int tlp_flags) * * If ACS redirects traffic at either divergence port, return * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE. If the ACS Control register cannot be - * read, return PCI_P2PDMA_MAP_NOT_SUPPORTED. Otherwise, return - * PCI_P2PDMA_MAP_BUS_ADDR. + * read, or Translation Blocking rejects the class being asked about, return + * PCI_P2PDMA_MAP_NOT_SUPPORTED. Otherwise, return PCI_P2PDMA_MAP_BUS_ADDR. * * Any two devices that have a data path that goes through the host bridge * will consult a whitelist. If the host bridge is in the whitelist, return @@ -945,6 +1030,8 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, if (!pci_acs_p2pdma_ctrl(b_child, &path.req_ctrl) && !path.unreadable) path.unreadable = b_child; + path.tb_below = pci_p2pdma_path_blocks_translation(client, + b_child, a); }

/*

From: Leon Romanovsky leonro@nvidia.com

mlx5_umem_needs_ats() enables ATS for any dma-buf whose caller asked for Relaxed Ordering, on the assumption that a switch in the path has CR, RR and DT all set. It also enables it for a buffer already mapped with the peer's bus addresses, which are not translatable at all.

P2PDMA has read the ACS controls, so ask it through dma_buf_p2pdma_map_type(): enable ATS only where the path is not routed directly as it stands, but would be for a Translated Request whose Completions carry Relaxed Ordering. Exporters that name no provider keep the old assumption, since their ACS settings remain hidden.

Signed-off-by: Leon Romanovsky leonro@nvidia.com --- drivers/infiniband/hw/mlx5/mlx5_ib.h | 36 ++------------------------------ drivers/infiniband/hw/mlx5/mr.c | 40 ++++++++++++++++++++++++++++++++++++ 2 files changed, 42 insertions(+), 34 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h index e9ddf2e97a76..ab32742b2180 100644 --- a/drivers/infiniband/hw/mlx5/mlx5_ib.h +++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h @@ -1646,40 +1646,8 @@ static inline bool rt_supported(int ts_cap) ts_cap == MLX5_TIMESTAMP_FORMAT_CAP_FREE_RUNNING_AND_REAL_TIME; }

-/* - * PCI Peer to Peer is a trainwreck. If no switch is present then things - * sometimes work, depending on the pci_distance_p2p logic for excluding broken - * root complexes. However if a switch is present in the path, then things get - * really ugly depending on how the switch is setup. This table assumes that the - * root complex is strict and is validating that all req/reps are matches - * perfectly - so any scenario where it sees only half the transaction is a - * failure. - * - * CR/RR/DT ATS RO P2P - * 00X X X OK - * 010 X X fails (request is routed to root but root never sees comp) - * 011 0 X fails (request is routed to root but root never sees comp) - * 011 1 X OK - * 10X X 1 OK - * 101 X 0 fails (completion is routed to root but root didn't see req) - * 110 X 0 SLOW - * 111 0 0 SLOW - * 111 1 0 fails (completion is routed to root but root didn't see req) - * 111 1 1 OK - * - * Unfortunately we cannot reliably know if a switch is present or what the - * CR/RR/DT ACS settings are, as in a VM that is all hidden. Assume that - * CR/RR/DT is 111 if the ATS cap is enabled and follow the last three rows. - * - * For now assume if the umem is a dma_buf then it is P2P. - */ -static inline bool mlx5_umem_needs_ats(struct mlx5_ib_dev *dev, - struct ib_umem *umem, int access_flags) -{ - if (!MLX5_CAP_GEN(dev->mdev, ats) || !umem->is_dmabuf) - return false; - return access_flags & IB_ACCESS_RELAXED_ORDERING; -} +bool mlx5_umem_needs_ats(struct mlx5_ib_dev *dev, struct ib_umem *umem, + int access_flags);

int set_roce_addr(struct mlx5_ib_dev *dev, u32 port_num, unsigned int index, const union ib_gid *gid, diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c index 00e13028762a..286f372e5b0c 100644 --- a/drivers/infiniband/hw/mlx5/mr.c +++ b/drivers/infiniband/hw/mlx5/mr.c @@ -38,6 +38,7 @@ #include <linux/export.h> #include <linux/delay.h> #include <linux/dma-buf.h> +#include <linux/dma-buf-mapping.h> #include <linux/dma-resv.h> #include <rdma/frmr_pools.h> #include <rdma/ib_umem_odp.h> @@ -47,6 +48,45 @@ #include "data_direct.h" #include "dmah.h"

+MODULE_IMPORT_NS("DMA_BUF"); + +bool mlx5_umem_needs_ats(struct mlx5_ib_dev *dev, struct ib_umem *umem, + int access_flags) +{ + struct dma_buf_attachment *attach; + + if (!MLX5_CAP_GEN(dev->mdev, ats) || !umem->is_dmabuf) + return false; + + /* + * The Completer decides whether its Completions carry Relaxed + * Ordering, and only a Request that asked for it can expect them to. + */ + if (!(access_flags & IB_ACCESS_RELAXED_ORDERING)) + return false; + + attach = to_ib_umem_dmabuf(umem)->attach; + switch (dma_buf_p2pdma_map_type(attach, 0)) { + case PCI_P2PDMA_MAP_NONE: + /* Nothing is known about the route, so fall back to the bet. */ + return true; + case PCI_P2PDMA_MAP_BUS_ADDR: + /* + * The path is routed directly already and is programmed with + * the peer's bus addresses. Those are not translatable, so + * ATS would be wrong as well as pointless. + */ + return false; + default: + break; + } + + return dma_buf_p2pdma_map_type(attach, + PCI_P2PDMA_TLP_TRANSLATED | + PCI_P2PDMA_TLP_RELAXED_CPL) == + PCI_P2PDMA_MAP_BUS_ADDR; +} + static int mkey_max_umr_order(struct mlx5_ib_dev *dev) { if (MLX5_CAP_GEN(dev->mdev, umr_extended_translation_offset))

On 9/14/26 13:22, Leon Romanovsky wrote:

From: Leon Romanovsky leonro@nvidia.com

Exporters keep the &struct p2pdma_provider backing a buffer in their own private data. An importer cannot reach it, so it has no way to learn how its own peer-to-peer traffic would be routed before it programs its hardware.

Add an optional @p2pdma_provider callback for an exporter to hand that provider out, and dma_buf_p2pdma_map_type() for an importer to ask by TLP class. Exporters keep the provider where it already lives, so this adds an operation rather than changing any existing signature or structure.

Signed-off-by: Leon Romanovsky leonro@nvidia.com

drivers/dma-buf/dma-buf-mapping.c | 32 +++++++++++++++++++++++ drivers/infiniband/core/uverbs_std_types_dmabuf.c | 12 +++++++++ drivers/vfio/pci/vfio_pci_dmabuf.c | 12 +++++++++ include/linux/dma-buf-mapping.h | 3 +++ include/linux/dma-buf.h | 17 ++++++++++++ 5 files changed, 76 insertions(+)

diff --git a/drivers/dma-buf/dma-buf-mapping.c b/drivers/dma-buf/dma-buf-mapping.c index 794acff2546a..fb03a698b381 100644 --- a/drivers/dma-buf/dma-buf-mapping.c +++ b/drivers/dma-buf/dma-buf-mapping.c @@ -6,6 +6,38 @@ #include <linux/dma-buf-mapping.h> #include <linux/dma-resv.h> +/**

• • dma_buf_p2pdma_map_type - How peer-to-peer traffic to a buffer is routed
• • @attach: attachment of the importer that will issue the traffic
• • @tlp_flags: &enum pci_p2pdma_tlp_flags describing the TLPs it will issue
• • Reports how the PCIe fabric routes @tlp_flags traffic between the buffer
• • behind @attach and the importer attached to it, so that an importer can
• • choose the TLP attributes that earn it a direct route before it programs
• • its hardware.
• • Return: the mapping type for @tlp_flags traffic, or PCI_P2PDMA_MAP_NONE
• • when the exporter names no &struct p2pdma_provider and nothing is known
• • about the route.
• */

+enum pci_p2pdma_map_type +dma_buf_p2pdma_map_type(struct dma_buf_attachment *attach,

• 	unsigned int tlp_flags)
  

+{

• struct dma_buf *dmabuf = attach->dmabuf;
• struct p2pdma_provider *provider;
• if (!dmabuf->ops->p2pdma_provider)

• return PCI_P2PDMA_MAP_NONE;
  

• provider = dmabuf->ops->p2pdma_provider(dmabuf);
• if (!provider)

• return PCI_P2PDMA_MAP_NONE;
  

• return pci_p2pdma_map_type_tlp(provider, attach->dev, tlp_flags);

Calling PCI subsystem functions from dma-buf is a hard NO-GO.

Then wrappers for DMA-buf backend functions should be in dma-buf.c and not here.

I shouldn't have allowed the mapping functions to be added to DMA-buf in the first place, all of this belongs either into the DMA layer or the exporter.

We should probably have a single callback the exporter provides to fill in a structure with PCI specific information for a mapping.

+} +EXPORT_SYMBOL_NS_GPL(dma_buf_p2pdma_map_type, "DMA_BUF");

static struct scatterlist *fill_sg_entry(struct scatterlist *sgl, size_t length, dma_addr_t addr) { diff --git a/drivers/infiniband/core/uverbs_std_types_dmabuf.c b/drivers/infiniband/core/uverbs_std_types_dmabuf.c index 2411ebee69e2..5a6a1ee430a7 100644 --- a/drivers/infiniband/core/uverbs_std_types_dmabuf.c +++ b/drivers/infiniband/core/uverbs_std_types_dmabuf.c @@ -76,6 +76,17 @@ static void uverbs_dmabuf_release(struct dma_buf *dmabuf) uverbs_uobject_release(&priv->uobj); } +static struct p2pdma_provider * +uverbs_dmabuf_provider(struct dma_buf *dmabuf) +{

• struct ib_uverbs_dmabuf_file *priv = dmabuf->priv;
• if (priv->revoked)

• return NULL;
  

• return priv->provider;

+}

static const struct dma_buf_ops uverbs_dmabuf_ops = { .attach = uverbs_dmabuf_attach, .map_dma_buf = uverbs_dmabuf_map, @@ -83,6 +94,7 @@ static const struct dma_buf_ops uverbs_dmabuf_ops = { .pin = uverbs_dmabuf_pin, .unpin = uverbs_dmabuf_unpin, .release = uverbs_dmabuf_release,

• .p2pdma_provider = uverbs_dmabuf_provider,

}; static int UVERBS_HANDLER(UVERBS_METHOD_DMABUF_ALLOC)( diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c index c16f460c01d6..fcf392cfc3c5 100644 --- a/drivers/vfio/pci/vfio_pci_dmabuf.c +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c @@ -99,11 +99,23 @@ static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf) kfree(priv); } +static struct p2pdma_provider * +vfio_pci_dma_buf_provider(struct dma_buf *dmabuf) +{

• struct vfio_pci_dma_buf *priv = dmabuf->priv;
• if (priv->revoked)

• return NULL;
  

• return priv->provider;

+}

static const struct dma_buf_ops vfio_pci_dmabuf_ops = { .attach = vfio_pci_dma_buf_attach, .map_dma_buf = vfio_pci_dma_buf_map, .unmap_dma_buf = vfio_pci_dma_buf_unmap, .release = vfio_pci_dma_buf_release,

• .p2pdma_provider = vfio_pci_dma_buf_provider,

Please split up the patch into the actual DMA-buf changes, exporter changes and importer changes.

Regards, Christian.

}; /* diff --git a/include/linux/dma-buf-mapping.h b/include/linux/dma-buf-mapping.h index 09bde3f748e4..37b3da10b17a 100644 --- a/include/linux/dma-buf-mapping.h +++ b/include/linux/dma-buf-mapping.h @@ -7,6 +7,9 @@ #define __DMA_BUF_MAPPING_H__ #include <linux/dma-buf.h> +enum pci_p2pdma_map_type +dma_buf_p2pdma_map_type(struct dma_buf_attachment *attach,

• 	unsigned int tlp_flags);
  

struct sg_table *dma_buf_phys_vec_to_sgt(struct dma_buf_attachment *attach, struct p2pdma_provider *provider, struct phys_vec *phys_vec, diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index d1203da56fc5..cff1ee0838f0 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -186,6 +186,23 @@ struct dma_buf_ops { * if the call would block. */

• /**

• * @p2pdma_provider:
  

• *
  

• * Returns the &struct p2pdma_provider backing this buffer, so that an
  

• * importer can ask how its peer-to-peer traffic would be routed before
  

• * it programs its hardware. Importers reach this through
  

• * dma_buf_p2pdma_map_type() rather than calling it directly.
  

• *
  

• * Exporters of MMIO memory that is reachable peer-to-peer should
  

• * implement this. This callback is optional.
  

• *
  

• * Returns:
  

• *
  

• * The provider backing the buffer.
  

• */
  

• struct p2pdma_provider *(*p2pdma_provider)(struct dma_buf *dmabuf);
• /**
  • @release: