The P2PDMA code currently provides two features under the same CONFIG_PCI_P2PDMA option:
1. Locate providers via pcim_p2pdma_provider() 2. Manage actual P2P DMA
Some drivers (such as vfio-pci) depend on (1), without having a hard dependency on (2).
A future vfio-pci commit will rely on pcim_p2pdma_provider() always being present. If that depended on CONFIG_PCI_P2PDMA, it would make vfio-pci only available if CONFIG_ZONE_DEVICE is present (e.g. 64-bit systems), even when P2P is not needed.
To resolve this, introduce CONFIG_PCI_P2PDMA_CORE and refactor the basic provider functionality into a new p2pdma_core.c file. This is available even if the CONFIG_PCI_P2PDMA feature is disabled (or unavailable due to !CONFIG_ZONE_DEVICE), satisfying (1).
Then, when the original CONFIG_PCI_P2PDMA is set, drivers have access to the additional P2P features of (2). This still depends on CONFIG_ZONE_DEVICE.
Signed-off-by: Matt Evans matt@ozlabs.org --- MAINTAINERS | 2 +- drivers/pci/Kconfig | 10 ++-- drivers/pci/Makefile | 1 + drivers/pci/p2pdma.c | 107 +-------------------------------- drivers/pci/p2pdma.h | 29 +++++++++ drivers/pci/p2pdma_core.c | 118 +++++++++++++++++++++++++++++++++++++ include/linux/pci-p2pdma.h | 24 ++++---- include/linux/pci.h | 2 +- 8 files changed, 171 insertions(+), 122 deletions(-) create mode 100644 drivers/pci/p2pdma.h create mode 100644 drivers/pci/p2pdma_core.c
diff --git a/MAINTAINERS b/MAINTAINERS index c8d4b913f26c..713861af4484 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -20626,7 +20626,7 @@ B: https://bugzilla.kernel.org C: irc://irc.oftc.net/linux-pci T: git git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git F: Documentation/driver-api/pci/p2pdma.rst -F: drivers/pci/p2pdma.c +F: drivers/pci/p2pdma* F: include/linux/pci-p2pdma.h
PCI POWER CONTROL diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig index 33c88432b728..59d70bc84cc9 100644 --- a/drivers/pci/Kconfig +++ b/drivers/pci/Kconfig @@ -206,11 +206,7 @@ config PCIE_TPH config PCI_P2PDMA bool "PCI peer-to-peer transfer support" depends on ZONE_DEVICE - # - # The need for the scatterlist DMA bus address flag means PCI P2PDMA - # requires 64bit - # - depends on 64BIT + select PCI_P2PDMA_CORE select GENERIC_ALLOCATOR select NEED_SG_DMA_FLAGS help @@ -226,6 +222,10 @@ config PCI_P2PDMA
If unsure, say N.
+config PCI_P2PDMA_CORE + default n + bool + config PCI_LABEL def_bool y if (DMI || ACPI) select NLS diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile index 41ebc3b9a518..0b32572d57a1 100644 --- a/drivers/pci/Makefile +++ b/drivers/pci/Makefile @@ -30,6 +30,7 @@ obj-$(CONFIG_PCI_SYSCALL) += syscall.o obj-$(CONFIG_PCI_STUB) += pci-stub.o obj-$(CONFIG_PCI_PF_STUB) += pci-pf-stub.o obj-$(CONFIG_PCI_ECAM) += ecam.o +obj-$(CONFIG_PCI_P2PDMA_CORE) += p2pdma_core.o obj-$(CONFIG_PCI_P2PDMA) += p2pdma.o obj-$(CONFIG_XEN_PCIDEV_FRONTEND) += xen-pcifront.o obj-$(CONFIG_VGA_ARB) += vgaarb.o diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index a5a1baebc34e..50b1a7daf55c 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -21,12 +21,7 @@ #include <linux/seq_buf.h> #include <linux/xarray.h>
-struct pci_p2pdma { - struct gen_pool *pool; - bool p2pmem_published; - struct xarray map_types; - struct p2pdma_provider mem[PCI_STD_NUM_BARS]; -}; +#include "p2pdma.h"
struct pci_p2pdma_pagemap { struct dev_pagemap pgmap; @@ -226,8 +221,7 @@ static const struct dev_pagemap_ops p2pdma_pgmap_ops = { .folio_free = p2pdma_folio_free, };
-static void pci_p2pdma_release_pool(struct pci_dev *pdev, - struct pci_p2pdma *p2pdma) +void pci_p2pdma_release_pool(struct pci_dev *pdev, struct pci_p2pdma *p2pdma) { if (!p2pdma->pool) return; @@ -237,103 +231,6 @@ static void pci_p2pdma_release_pool(struct pci_dev *pdev, sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group); }
-static void pci_p2pdma_release(void *data) -{ - struct pci_dev *pdev = data; - struct pci_p2pdma *p2pdma; - - p2pdma = rcu_dereference_protected(pdev->p2pdma, 1); - if (!p2pdma) - return; - - /* Flush and disable pci_alloc_p2p_mem() */ - pdev->p2pdma = NULL; - pci_p2pdma_release_pool(pdev, p2pdma); - xa_destroy(&p2pdma->map_types); -} - -/** - * pcim_p2pdma_init - Initialise peer-to-peer DMA providers - * @pdev: The PCI device to enable P2PDMA for - * - * This function initializes the peer-to-peer DMA infrastructure - * for a PCI device. It allocates and sets up the necessary data - * structures to support P2PDMA operations, including mapping type - * tracking. - */ -int pcim_p2pdma_init(struct pci_dev *pdev) -{ - struct pci_p2pdma *p2p; - int i, ret; - - p2p = rcu_dereference_protected(pdev->p2pdma, 1); - if (p2p) - return 0; - - p2p = devm_kzalloc(&pdev->dev, sizeof(*p2p), GFP_KERNEL); - if (!p2p) - return -ENOMEM; - - xa_init(&p2p->map_types); - /* - * Iterate over all standard PCI BARs and record only those that - * correspond to MMIO regions. Skip non-memory resources (e.g. I/O - * port BARs) since they cannot be used for peer-to-peer (P2P) - * transactions. - */ - for (i = 0; i < PCI_STD_NUM_BARS; i++) { - if (!(pci_resource_flags(pdev, i) & IORESOURCE_MEM)) - continue; - - p2p->mem[i].owner = &pdev->dev; - p2p->mem[i].bus_offset = - pci_bus_address(pdev, i) - pci_resource_start(pdev, i); - } - - ret = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_release, pdev); - if (ret) - goto out_p2p; - - rcu_assign_pointer(pdev->p2pdma, p2p); - return 0; - -out_p2p: - devm_kfree(&pdev->dev, p2p); - return ret; -} -EXPORT_SYMBOL_GPL(pcim_p2pdma_init); - -/** - * pcim_p2pdma_provider - Get peer-to-peer DMA provider - * @pdev: The PCI device to enable P2PDMA for - * @bar: BAR index to get provider - * - * This function gets peer-to-peer DMA provider for a PCI device. The lifetime - * of the provider (and of course the MMIO) is bound to the lifetime of the - * driver. A driver calling this function must ensure that all references to the - * provider, and any DMA mappings created for any MMIO, are all cleaned up - * before the driver remove() completes. - * - * Since P2P is almost always shared with a second driver this means some system - * to notify, invalidate and revoke the MMIO's DMA must be in place to use this - * function. For example a revoke can be built using DMABUF. - */ -struct p2pdma_provider *pcim_p2pdma_provider(struct pci_dev *pdev, int bar) -{ - struct pci_p2pdma *p2p; - - if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM)) - return NULL; - - p2p = rcu_dereference_protected(pdev->p2pdma, 1); - if (WARN_ON(!p2p)) - /* Someone forgot to call to pcim_p2pdma_init() before */ - return NULL; - - return &p2p->mem[bar]; -} -EXPORT_SYMBOL_GPL(pcim_p2pdma_provider); - static int pci_p2pdma_setup_pool(struct pci_dev *pdev) { struct pci_p2pdma *p2pdma; diff --git a/drivers/pci/p2pdma.h b/drivers/pci/p2pdma.h new file mode 100644 index 000000000000..946383809981 --- /dev/null +++ b/drivers/pci/p2pdma.h @@ -0,0 +1,29 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * PCI peer-to-peer DMA support. + */ + +#ifndef _PCI_P2PDMA_H +#define _PCI_P2PDMA_H + +#include <linux/genalloc.h> +#include <linux/pci-p2pdma.h> +#include <linux/xarray.h> + +struct pci_p2pdma { + struct gen_pool *pool; + bool p2pmem_published; + struct xarray map_types; + struct p2pdma_provider mem[PCI_STD_NUM_BARS]; +}; + +#ifdef CONFIG_PCI_P2PDMA +void pci_p2pdma_release_pool(struct pci_dev *pdev, struct pci_p2pdma *p2pdma); +#else +static inline void pci_p2pdma_release_pool(struct pci_dev *pdev, + struct pci_p2pdma *p2pdma) +{ +} +#endif + +#endif diff --git a/drivers/pci/p2pdma_core.c b/drivers/pci/p2pdma_core.c new file mode 100644 index 000000000000..bb2138bf2bc7 --- /dev/null +++ b/drivers/pci/p2pdma_core.c @@ -0,0 +1,118 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * PCI peer-to-peer DMA support core, providing a bare-bones + * pcim_p2pdma_provider() interface to drivers even if full P2PDMA + * isn't present. The full P2PDMA feature is in p2pdma.c (see + * CONFIG_PCI_P2PDMA). + * + * Copyright (c) 2016-2018, Logan Gunthorpe + * Copyright (c) 2016-2017, Microsemi Corporation + * Copyright (c) 2017, Christoph Hellwig + * Copyright (c) 2018, Eideticom Inc. + */ + +#define pr_fmt(fmt) "pci-p2pdma: " fmt +#include <linux/ctype.h> +#include <linux/genalloc.h> +#include <linux/memremap.h> +#include <linux/pci-p2pdma.h> +#include <linux/xarray.h> + +#include "p2pdma.h" + +static void pci_p2pdma_release(void *data) +{ + struct pci_dev *pdev = data; + struct pci_p2pdma *p2pdma; + + p2pdma = rcu_dereference_protected(pdev->p2pdma, 1); + if (!p2pdma) + return; + + /* Flush and disable pci_alloc_p2p_mem() */ + pdev->p2pdma = NULL; + pci_p2pdma_release_pool(pdev, p2pdma); + xa_destroy(&p2pdma->map_types); +} + +/** + * pcim_p2pdma_init - Initialise peer-to-peer DMA providers + * @pdev: The PCI device to enable P2PDMA for + * + * This function initializes the peer-to-peer DMA infrastructure + * for a PCI device. It allocates and sets up the necessary data + * structures to support P2PDMA operations, including mapping type + * tracking. + */ +int pcim_p2pdma_init(struct pci_dev *pdev) +{ + struct pci_p2pdma *p2p; + int i, ret; + + p2p = rcu_dereference_protected(pdev->p2pdma, 1); + if (p2p) + return 0; + + p2p = devm_kzalloc(&pdev->dev, sizeof(*p2p), GFP_KERNEL); + if (!p2p) + return -ENOMEM; + + xa_init(&p2p->map_types); + /* + * Iterate over all standard PCI BARs and record only those that + * correspond to MMIO regions. Skip non-memory resources (e.g. I/O + * port BARs) since they cannot be used for peer-to-peer (P2P) + * transactions. + */ + for (i = 0; i < PCI_STD_NUM_BARS; i++) { + if (!(pci_resource_flags(pdev, i) & IORESOURCE_MEM)) + continue; + + p2p->mem[i].owner = &pdev->dev; + p2p->mem[i].bus_offset = + pci_bus_address(pdev, i) - pci_resource_start(pdev, i); + } + + ret = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_release, pdev); + if (ret) + goto out_p2p; + + rcu_assign_pointer(pdev->p2pdma, p2p); + return 0; + +out_p2p: + devm_kfree(&pdev->dev, p2p); + return ret; +} +EXPORT_SYMBOL_GPL(pcim_p2pdma_init); + +/** + * pcim_p2pdma_provider - Get peer-to-peer DMA provider + * @pdev: The PCI device to enable P2PDMA for + * @bar: BAR index to get provider + * + * This function gets peer-to-peer DMA provider for a PCI device. The lifetime + * of the provider (and of course the MMIO) is bound to the lifetime of the + * driver. A driver calling this function must ensure that all references to the + * provider, and any DMA mappings created for any MMIO, are all cleaned up + * before the driver remove() completes. + * + * Since P2P is almost always shared with a second driver this means some system + * to notify, invalidate and revoke the MMIO's DMA must be in place to use this + * function. For example a revoke can be built using DMABUF. + */ +struct p2pdma_provider *pcim_p2pdma_provider(struct pci_dev *pdev, int bar) +{ + struct pci_p2pdma *p2p; + + if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM)) + return NULL; + + p2p = rcu_dereference_protected(pdev->p2pdma, 1); + if (WARN_ON(!p2p)) + /* Someone forgot to call to pcim_p2pdma_init() before */ + return NULL; + + return &p2p->mem[bar]; +} +EXPORT_SYMBOL_GPL(pcim_p2pdma_provider); diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h index 873de20a2247..4c42a7b2ee85 100644 --- a/include/linux/pci-p2pdma.h +++ b/include/linux/pci-p2pdma.h @@ -67,9 +67,22 @@ enum pci_p2pdma_map_type { PCI_P2PDMA_MAP_THRU_HOST_BRIDGE, };
-#ifdef CONFIG_PCI_P2PDMA +#ifdef CONFIG_PCI_P2PDMA_CORE int pcim_p2pdma_init(struct pci_dev *pdev); struct p2pdma_provider *pcim_p2pdma_provider(struct pci_dev *pdev, int bar); +#else +static inline int pcim_p2pdma_init(struct pci_dev *pdev) +{ + return -EOPNOTSUPP; +} +static inline struct p2pdma_provider *pcim_p2pdma_provider(struct pci_dev *pdev, + int bar) +{ + return NULL; +} +#endif + +#ifdef CONFIG_PCI_P2PDMA int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size, u64 offset); int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients, @@ -89,15 +102,6 @@ ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev, enum pci_p2pdma_map_type pci_p2pdma_map_type(struct p2pdma_provider *provider, struct device *dev); #else /* CONFIG_PCI_P2PDMA */ -static inline int pcim_p2pdma_init(struct pci_dev *pdev) -{ - return -EOPNOTSUPP; -} -static inline struct p2pdma_provider *pcim_p2pdma_provider(struct pci_dev *pdev, - int bar) -{ - return NULL; -} static inline int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size, u64 offset) { diff --git a/include/linux/pci.h b/include/linux/pci.h index 2c4454583c11..531aec355686 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -557,7 +557,7 @@ struct pci_dev { u16 pasid_cap; /* PASID Capability offset */ u16 pasid_features; #endif -#ifdef CONFIG_PCI_P2PDMA +#ifdef CONFIG_PCI_P2PDMA_CORE struct pci_p2pdma __rcu *p2pdma; #endif #ifdef CONFIG_PCI_DOE