Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932162AbbLMV2i (ORCPT ); Sun, 13 Dec 2015 16:28:38 -0500 Received: from mail-pa0-f51.google.com ([209.85.220.51]:33568 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932137AbbLMV2e (ORCPT ); Sun, 13 Dec 2015 16:28:34 -0500 Subject: [RFC PATCH 3/3] x86: Create dma_mark_dirty to dirty pages used for DMA by VM guest From: Alexander Duyck To: kvm@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, alexander.duyck@gmail.com, qemu-devel@nongnu.org Cc: tianyu.lan@intel.com, yang.zhang.wz@gmail.com, mst@redhat.com, konrad.wilk@oracle.com, dgilbert@redhat.com, agraf@suse.de, alex.williamson@redhat.com Date: Sun, 13 Dec 2015 13:28:31 -0800 Message-ID: <20151213212831.5410.84365.stgit@localhost.localdomain> In-Reply-To: <20151213212557.5410.48577.stgit@localhost.localdomain> References: <20151213212557.5410.48577.stgit@localhost.localdomain> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8992 Lines: 231 This patch is meant to provide the guest with a way of flagging DMA pages as being dirty to the host when using a direct-assign device within a guest. The advantage to this approach is that it is fairly simple, however It currently has a singificant impact on device performance in all the scenerios where it won't be needed. As such this is really meant only as a proof of concept and to get the ball rolling in terms of figuring out how best to approach the issue of dirty page tracking for a guest that is using a direct assigned device. In addition with just this patch it should be possible to modify current migration approaches so that instead of having to hot-remove the device before starting the migration this can instead be delayed until the period before the final stop and copy. Signed-off-by: Alexander Duyck --- arch/arm/include/asm/dma-mapping.h | 3 ++- arch/arm64/include/asm/dma-mapping.h | 5 ++--- arch/ia64/include/asm/dma.h | 1 + arch/mips/include/asm/dma-mapping.h | 1 + arch/powerpc/include/asm/swiotlb.h | 1 + arch/tile/include/asm/dma-mapping.h | 1 + arch/unicore32/include/asm/dma-mapping.h | 1 + arch/x86/Kconfig | 11 +++++++++++ arch/x86/include/asm/swiotlb.h | 26 ++++++++++++++++++++++++++ drivers/xen/swiotlb-xen.c | 6 ++++++ lib/swiotlb.c | 6 ++++++ 11 files changed, 58 insertions(+), 4 deletions(-) diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h index ccb3aa64640d..1962d7b471c7 100644 --- a/arch/arm/include/asm/dma-mapping.h +++ b/arch/arm/include/asm/dma-mapping.h @@ -167,7 +167,8 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size) return 1; } -static inline void dma_mark_clean(void *addr, size_t size) { } +static inline void dma_mark_clean(void *addr, size_t size) {} +static inline void dma_mark_dirty(void *addr, size_t size) {} extern int arm_dma_set_mask(struct device *dev, u64 dma_mask); diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h index 61e08f360e31..8d24fe11c8a3 100644 --- a/arch/arm64/include/asm/dma-mapping.h +++ b/arch/arm64/include/asm/dma-mapping.h @@ -84,9 +84,8 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size) return addr + size - 1 <= *dev->dma_mask; } -static inline void dma_mark_clean(void *addr, size_t size) -{ -} +static inline void dma_mark_clean(void *addr, size_t size) {} +static inline void dma_mark_dirty(void *addr, size_t size) {} #endif /* __KERNEL__ */ #endif /* __ASM_DMA_MAPPING_H */ diff --git a/arch/ia64/include/asm/dma.h b/arch/ia64/include/asm/dma.h index 4d97f60f1ef5..d92ebeb2758e 100644 --- a/arch/ia64/include/asm/dma.h +++ b/arch/ia64/include/asm/dma.h @@ -20,5 +20,6 @@ extern unsigned long MAX_DMA_ADDRESS; #define free_dma(x) void dma_mark_clean(void *addr, size_t size); +static inline void dma_mark_dirty(void *addr, size_t size) {} #endif /* _ASM_IA64_DMA_H */ diff --git a/arch/mips/include/asm/dma-mapping.h b/arch/mips/include/asm/dma-mapping.h index e604f760c4a0..567f6e03e337 100644 --- a/arch/mips/include/asm/dma-mapping.h +++ b/arch/mips/include/asm/dma-mapping.h @@ -28,6 +28,7 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size) } static inline void dma_mark_clean(void *addr, size_t size) {} +static inline void dma_mark_dirty(void *addr, size_t size) {} #include diff --git a/arch/powerpc/include/asm/swiotlb.h b/arch/powerpc/include/asm/swiotlb.h index de99d6e29430..b694e8399e28 100644 --- a/arch/powerpc/include/asm/swiotlb.h +++ b/arch/powerpc/include/asm/swiotlb.h @@ -16,6 +16,7 @@ extern struct dma_map_ops swiotlb_dma_ops; static inline void dma_mark_clean(void *addr, size_t size) {} +static inline void dma_mark_dirty(void *addr, size_t size) {} extern unsigned int ppc_swiotlb_enable; int __init swiotlb_setup_bus_notifier(void); diff --git a/arch/tile/include/asm/dma-mapping.h b/arch/tile/include/asm/dma-mapping.h index 96ac6cce4a32..79953f09e938 100644 --- a/arch/tile/include/asm/dma-mapping.h +++ b/arch/tile/include/asm/dma-mapping.h @@ -58,6 +58,7 @@ static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr) } static inline void dma_mark_clean(void *addr, size_t size) {} +static inline void dma_mark_dirty(void *addr, size_t size) {} static inline void set_dma_ops(struct device *dev, struct dma_map_ops *ops) { diff --git a/arch/unicore32/include/asm/dma-mapping.h b/arch/unicore32/include/asm/dma-mapping.h index 8140e053ccd3..b9d357ab122d 100644 --- a/arch/unicore32/include/asm/dma-mapping.h +++ b/arch/unicore32/include/asm/dma-mapping.h @@ -49,6 +49,7 @@ static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr) } static inline void dma_mark_clean(void *addr, size_t size) {} +static inline void dma_mark_dirty(void *addr, size_t size) {} static inline void dma_cache_sync(struct device *dev, void *vaddr, size_t size, enum dma_data_direction direction) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index db3622f22b61..f0b09156d7d8 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -841,6 +841,17 @@ config SWIOTLB with more than 3 GB of memory. If unsure, say Y. +config SWIOTLB_PAGE_DIRTYING + bool "SWIOTLB page dirtying" + depends on SWIOTLB + default n + ---help--- + SWIOTLB page dirtying support provides a means for the guest to + trigger write faults on pages which received DMA from the device + without changing the data contained within. By doing this the + guest can then support migration assuming the device and any + remaining pages are unmapped prior to the CPU itself being halted. + config IOMMU_HELPER def_bool y depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU diff --git a/arch/x86/include/asm/swiotlb.h b/arch/x86/include/asm/swiotlb.h index ab05d73e2bb7..7f9f2e76d081 100644 --- a/arch/x86/include/asm/swiotlb.h +++ b/arch/x86/include/asm/swiotlb.h @@ -29,6 +29,32 @@ static inline void pci_swiotlb_late_init(void) static inline void dma_mark_clean(void *addr, size_t size) {} +/* + * Make certain that the pages get marked as dirty + * now that the device has completed the DMA transaction. + * + * Without this we run the risk of a guest migration missing + * the pages that the device has written to as they are not + * tracked as a part of the dirty page tracking. + */ +static inline void dma_mark_dirty(void *addr, size_t size) +{ +#ifdef CONFIG_SWIOTLB_PAGE_DIRTYING + unsigned long pg_addr, start; + + start = (unsigned long)addr; + pg_addr = PAGE_ALIGN(start + size); + start &= ~(sizeof(atomic_t) - 1); + + /* trigger a write fault on each page, excluding first page */ + while ((pg_addr -= PAGE_SIZE) > start) + atomic_add(0, (atomic_t *)pg_addr); + + /* trigger a write fault on first word of DMA */ + atomic_add(0, (atomic_t *)start); +#endif /* CONFIG_SWIOTLB_PAGE_DIRTYING */ +} + extern void *x86_swiotlb_alloc_coherent(struct device *hwdev, size_t size, dma_addr_t *dma_handle, gfp_t flags, struct dma_attrs *attrs); diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c index 2154c70e47da..1533b3eefb67 100644 --- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -456,6 +456,9 @@ void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr, */ if (dir == DMA_FROM_DEVICE) dma_mark_clean(phys_to_virt(paddr), size); + + if (dir != DMA_TO_DEVICE) + dma_mark_dirty(phys_to_virt(paddr), size); } EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_page); @@ -485,6 +488,9 @@ xen_swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr, if (dir == DMA_FROM_DEVICE) dma_mark_clean(phys_to_virt(paddr), size); + + if (dir != DMA_TO_DEVICE) + dma_mark_dirty(phys_to_virt(paddr), size); } EXPORT_SYMBOL_GPL(xen_swiotlb_sync_single_for_cpu); diff --git a/lib/swiotlb.c b/lib/swiotlb.c index 384ac06217b2..4223d6c54724 100644 --- a/lib/swiotlb.c +++ b/lib/swiotlb.c @@ -802,6 +802,9 @@ void swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr, */ if (dir == DMA_FROM_DEVICE) dma_mark_clean(phys_to_virt(paddr), size); + + if (dir != DMA_TO_DEVICE) + dma_mark_dirty(phys_to_virt(paddr), size); } EXPORT_SYMBOL_GPL(swiotlb_unmap_page); @@ -830,6 +833,9 @@ swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr, if (dir == DMA_FROM_DEVICE) dma_mark_clean(phys_to_virt(paddr), size); + + if (dir != DMA_TO_DEVICE) + dma_mark_dirty(phys_to_virt(paddr), size); } EXPORT_SYMBOL(swiotlb_sync_single_for_cpu); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/