From: David Woodhouse dwmw@amazon.co.uk

[ Upstream commit 3499ba8198cad47b731792e5e56b9ec2a78a83a2 ]

For a while, event channel notification via the PCI platform device has been broken, because we attempt to communicate with xenstore before we even have notifications working, with the xs_reset_watches() call in xs_init().

We tend to get away with this on Xen versions below 4.0 because we avoid calling xs_reset_watches() anyway, because xenstore might not cope with reading a non-existent key. And newer Xen *does* have the vector callback support, so we rarely fall back to INTX/GSI delivery.

To fix it, clean up a bit of the mess of xs_init() and xenbus_probe() startup. Call xs_init() directly from xenbus_init() only in the !XS_HVM case, deferring it to be called from xenbus_probe() in the XS_HVM case instead.

Then fix up the invocation of xenbus_probe() to happen either from its device_initcall if the callback is available early enough, or when the callback is finally set up. This means that the hack of calling xenbus_probe() from a workqueue after the first interrupt, or directly from the PCI platform device setup, is no longer needed.

Signed-off-by: David Woodhouse dwmw@amazon.co.uk Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.com Link: https://lore.kernel.org/r/20210113132606.422794-2-dwmw2@infradead.org Signed-off-by: Juergen Gross jgross@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm/xen/enlighten.c | 2 +- drivers/xen/events/events_base.c | 10 ---- drivers/xen/platform-pci.c | 1 - drivers/xen/xenbus/xenbus.h | 1 + drivers/xen/xenbus/xenbus_comms.c | 8 --- drivers/xen/xenbus/xenbus_probe.c | 81 +++++++++++++++++++++++++------ include/xen/xenbus.h | 2 +- 7 files changed, 70 insertions(+), 35 deletions(-)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c index ba7f4c8f5c3e4..e8e637c4f354d 100644 --- a/arch/arm/xen/enlighten.c +++ b/arch/arm/xen/enlighten.c @@ -393,7 +393,7 @@ static int __init xen_guest_init(void) } gnttab_init(); if (!xen_initial_domain()) - xenbus_probe(NULL); + xenbus_probe();

/* * Making sure board specific code will not set up ops for diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c index aca8456752797..8c08c7d46d3d0 100644 --- a/drivers/xen/events/events_base.c +++ b/drivers/xen/events/events_base.c @@ -1987,16 +1987,6 @@ static struct irq_chip xen_percpu_chip __read_mostly = { .irq_ack = ack_dynirq, };

-int xen_set_callback_via(uint64_t via) -{ - struct xen_hvm_param a; - a.domid = DOMID_SELF; - a.index = HVM_PARAM_CALLBACK_IRQ; - a.value = via; - return HYPERVISOR_hvm_op(HVMOP_set_param, &a); -} -EXPORT_SYMBOL_GPL(xen_set_callback_via); - #ifdef CONFIG_XEN_PVHVM /* Vector callbacks are better than PCI interrupts to receive event * channel notifications because we can receive vector callbacks on any diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c index 5d7dcad0b0a0d..4cec8146609ad 100644 --- a/drivers/xen/platform-pci.c +++ b/drivers/xen/platform-pci.c @@ -162,7 +162,6 @@ static int platform_pci_probe(struct pci_dev *pdev, ret = gnttab_init(); if (ret) goto grant_out; - xenbus_probe(NULL); return 0; grant_out: gnttab_free_auto_xlat_frames(); diff --git a/drivers/xen/xenbus/xenbus.h b/drivers/xen/xenbus/xenbus.h index 139539b0ab20d..e6a8d02d35254 100644 --- a/drivers/xen/xenbus/xenbus.h +++ b/drivers/xen/xenbus/xenbus.h @@ -114,6 +114,7 @@ int xenbus_probe_node(struct xen_bus_type *bus, const char *type, const char *nodename); int xenbus_probe_devices(struct xen_bus_type *bus); +void xenbus_probe(void);

void xenbus_dev_changed(const char *node, struct xen_bus_type *bus);

diff --git a/drivers/xen/xenbus/xenbus_comms.c b/drivers/xen/xenbus/xenbus_comms.c index eb5151fc8efab..e5fda0256feb3 100644 --- a/drivers/xen/xenbus/xenbus_comms.c +++ b/drivers/xen/xenbus/xenbus_comms.c @@ -57,16 +57,8 @@ DEFINE_MUTEX(xs_response_mutex); static int xenbus_irq; static struct task_struct *xenbus_task;

-static DECLARE_WORK(probe_work, xenbus_probe); - - static irqreturn_t wake_waiting(int irq, void *unused) { - if (unlikely(xenstored_ready == 0)) { - xenstored_ready = 1; - schedule_work(&probe_work); - } - wake_up(&xb_waitq); return IRQ_HANDLED; } diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c index 217bcc092a968..fe24e8dcb2b8e 100644 --- a/drivers/xen/xenbus/xenbus_probe.c +++ b/drivers/xen/xenbus/xenbus_probe.c @@ -674,29 +674,76 @@ void unregister_xenstore_notifier(struct notifier_block *nb) } EXPORT_SYMBOL_GPL(unregister_xenstore_notifier);

-void xenbus_probe(struct work_struct *unused) +void xenbus_probe(void) { xenstored_ready = 1;

+ /* + * In the HVM case, xenbus_init() deferred its call to + * xs_init() in case callbacks were not operational yet. + * So do it now. + */ + if (xen_store_domain_type == XS_HVM) + xs_init(); + /* Notify others that xenstore is up */ blocking_notifier_call_chain(&xenstore_chain, 0, NULL); } -EXPORT_SYMBOL_GPL(xenbus_probe);

-static int __init xenbus_probe_initcall(void) +/* + * Returns true when XenStore init must be deferred in order to + * allow the PCI platform device to be initialised, before we + * can actually have event channel interrupts working. + */ +static bool xs_hvm_defer_init_for_callback(void) { - if (!xen_domain()) - return -ENODEV; +#ifdef CONFIG_XEN_PVHVM + return xen_store_domain_type == XS_HVM && + !xen_have_vector_callback; +#else + return false; +#endif +}

- if (xen_initial_domain() || xen_hvm_domain()) - return 0; +static int __init xenbus_probe_initcall(void) +{ + /* + * Probe XenBus here in the XS_PV case, and also XS_HVM unless we + * need to wait for the platform PCI device to come up. + */ + if (xen_store_domain_type == XS_PV || + (xen_store_domain_type == XS_HVM && + !xs_hvm_defer_init_for_callback())) + xenbus_probe();

- xenbus_probe(NULL); return 0; } - device_initcall(xenbus_probe_initcall);

+int xen_set_callback_via(uint64_t via) +{ + struct xen_hvm_param a; + int ret; + + a.domid = DOMID_SELF; + a.index = HVM_PARAM_CALLBACK_IRQ; + a.value = via; + + ret = HYPERVISOR_hvm_op(HVMOP_set_param, &a); + if (ret) + return ret; + + /* + * If xenbus_probe_initcall() deferred the xenbus_probe() + * due to the callback not functioning yet, we can do it now. + */ + if (!xenstored_ready && xs_hvm_defer_init_for_callback()) + xenbus_probe(); + + return ret; +} +EXPORT_SYMBOL_GPL(xen_set_callback_via); + /* Set up event channel for xenstored which is run as a local process * (this is normally used only in dom0) */ @@ -810,11 +857,17 @@ static int __init xenbus_init(void) break; }

- /* Initialize the interface to xenstore. */ - err = xs_init(); - if (err) { - pr_warn("Error initializing xenstore comms: %i\n", err); - goto out_error; + /* + * HVM domains may not have a functional callback yet. In that + * case let xs_init() be called from xenbus_probe(), which will + * get invoked at an appropriate time. + */ + if (xen_store_domain_type != XS_HVM) { + err = xs_init(); + if (err) { + pr_warn("Error initializing xenstore comms: %i\n", err); + goto out_error; + } }

if ((xen_store_domain_type != XS_LOCAL) && diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h index eba01ab5a55e0..fe9a9fa2ebc45 100644 --- a/include/xen/xenbus.h +++ b/include/xen/xenbus.h @@ -187,7 +187,7 @@ void xs_suspend_cancel(void);

struct work_struct;

-void xenbus_probe(struct work_struct *); +void xenbus_probe(void);

#define XENBUS_IS_ERR_READ(str) ({ \ if (!IS_ERR(str) && strlen(str) == 0) { \