From ac1bf3edcd2b807cf81ada500716f13b1394d58e Mon Sep 17 00:00:00 2001 From: Zenghui Yu Date: Sat, 8 May 2021 17:31:04 +0800 Subject: [PATCH] vfio: Maintain DMA mapping range for the container When synchronizing dirty bitmap from kernel VFIO we do it in a per-iova-range fashion and we allocate the userspace bitmap for each of the ioctl. This patch introduces `struct VFIODMARange` to describe a range of the given DMA mapping with respect to a VFIO_IOMMU_MAP_DMA operation, and make the bitmap cache of this range be persistent so that we don't need to g_try_malloc0() every time. Note that the new structure is almost a copy of `struct vfio_iommu_type1_dma_map` but only internally used by QEMU. More importantly, the cached per-iova-range dirty bitmap will be further used when we want to add support for the CLEAR_BITMAP and this cached bitmap will be used to guarantee we don't clear any unknown dirty bits otherwise that can be a severe data loss issue for migration code. It's pretty intuitive to maintain a bitmap per container since we perform log_sync at this granule. But I don't know how to deal with things like memory hot-{un}plug, sparse DMA mappings, etc. Suggestions welcome. * yet something to-do: - can't work with guest viommu - no locks - etc [ The idea and even the commit message are largely inherited from kvm side. See commit 9f4bf4baa8b820c7930e23c9566c9493db7e1d25. ] Signed-off-by: Zenghui Yu Signed-off-by: Kunkun Jiang --- hw/vfio/common.c | 62 +++++++++++++++++++++++++++++++---- include/hw/vfio/vfio-common.h | 9 +++++ 2 files changed, 65 insertions(+), 6 deletions(-) diff --git a/hw/vfio/common.c b/hw/vfio/common.c index 080046e3f5..86ea784919 100644 --- a/hw/vfio/common.c +++ b/hw/vfio/common.c @@ -445,6 +445,29 @@ unmap_exit: return ret; } +static VFIODMARange *vfio_lookup_match_range(VFIOContainer *container, + hwaddr start_addr, hwaddr size) +{ + VFIODMARange *qrange; + + QLIST_FOREACH(qrange, &container->dma_list, next) { + if (qrange->iova == start_addr && qrange->size == size) { + return qrange; + } + } + return NULL; +} + +static void vfio_dma_range_init_dirty_bitmap(VFIODMARange *qrange) +{ + uint64_t pages, size; + + pages = REAL_HOST_PAGE_ALIGN(qrange->size) / qemu_real_host_page_size; + size = ROUND_UP(pages, sizeof(__u64) * BITS_PER_BYTE) / BITS_PER_BYTE; + + qrange->bitmap = g_malloc0(size); +} + /* * DMA - Mapping and unmapping for the "type1" IOMMU interface used on x86 */ @@ -458,12 +481,29 @@ static int vfio_dma_unmap(VFIOContainer *container, .iova = iova, .size = size, }; + VFIODMARange *qrange; if (iotlb && container->dirty_pages_supported && vfio_devices_all_running_and_saving(container)) { return vfio_dma_unmap_bitmap(container, iova, size, iotlb); } + /* + * unregister the DMA range + * + * It seems that the memory layer will give us the same section as the one + * used in region_add(). Otherwise it'll be complicated to manipulate the + * bitmap across region_{add,del}. Is there any guarantee? + * + * But there is really not such a restriction on the kernel interface + * (VFIO_IOMMU_DIRTY_PAGES_FLAG_{UN}MAP_DMA, etc). + */ + qrange = vfio_lookup_match_range(container, iova, size); + assert(qrange); + g_free(qrange->bitmap); + QLIST_REMOVE(qrange, next); + g_free(qrange); + while (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) { /* * The type1 backend has an off-by-one bug in the kernel (71a7d3d78e3c @@ -500,6 +540,14 @@ static int vfio_dma_map(VFIOContainer *container, hwaddr iova, .iova = iova, .size = size, }; + VFIODMARange *qrange; + + qrange = g_malloc0(sizeof(*qrange)); + qrange->iova = iova; + qrange->size = size; + QLIST_INSERT_HEAD(&container->dma_list, qrange, next); + /* XXX allocate the dirty bitmap on demand */ + vfio_dma_range_init_dirty_bitmap(qrange); if (!readonly) { map.flags |= VFIO_DMA_MAP_FLAG_WRITE; @@ -1256,9 +1304,14 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova, { struct vfio_iommu_type1_dirty_bitmap *dbitmap; struct vfio_iommu_type1_dirty_bitmap_get *range; + VFIODMARange *qrange; uint64_t pages; int ret; + qrange = vfio_lookup_match_range(container, iova, size); + /* the same as vfio_dma_unmap() */ + assert(qrange); + dbitmap = g_malloc0(sizeof(*dbitmap) + sizeof(*range)); dbitmap->argsz = sizeof(*dbitmap) + sizeof(*range); @@ -1277,11 +1330,8 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova, pages = REAL_HOST_PAGE_ALIGN(range->size) / qemu_real_host_page_size; range->bitmap.size = ROUND_UP(pages, sizeof(__u64) * BITS_PER_BYTE) / BITS_PER_BYTE; - range->bitmap.data = g_try_malloc0(range->bitmap.size); - if (!range->bitmap.data) { - ret = -ENOMEM; - goto err_out; - } + + range->bitmap.data = (__u64 *)qrange->bitmap; ret = ioctl(container->fd, VFIO_IOMMU_DIRTY_PAGES, dbitmap); if (ret) { @@ -1297,7 +1347,6 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova, trace_vfio_get_dirty_bitmap(container->fd, range->iova, range->size, range->bitmap.size, ram_addr); err_out: - g_free(range->bitmap.data); g_free(dbitmap); return ret; @@ -2061,6 +2110,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as, QLIST_INIT(&container->giommu_list); QLIST_INIT(&container->hostwin_list); QLIST_INIT(&container->vrdl_list); + QLIST_INIT(&container->dma_list); ret = vfio_init_container(container, group->fd, errp); if (ret) { diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h index 8af11b0a76..20b9c8a1d3 100644 --- a/include/hw/vfio/vfio-common.h +++ b/include/hw/vfio/vfio-common.h @@ -76,6 +76,14 @@ typedef struct VFIOAddressSpace { struct VFIOGroup; +typedef struct VFIODMARange { + QLIST_ENTRY(VFIODMARange) next; + hwaddr iova; + size_t size; + void *vaddr; /* unused */ + unsigned long *bitmap; /* dirty bitmap cache for this range */ +} VFIODMARange; + typedef struct VFIOContainer { VFIOAddressSpace *space; int fd; /* /dev/vfio/vfio, empowered by the attached groups */ @@ -93,6 +101,7 @@ typedef struct VFIOContainer { QLIST_HEAD(, VFIOHostDMAWindow) hostwin_list; QLIST_HEAD(, VFIOGroup) group_list; QLIST_HEAD(, VFIORamDiscardListener) vrdl_list; + QLIST_HEAD(, VFIODMARange) dma_list; QLIST_ENTRY(VFIOContainer) next; } VFIOContainer; -- 2.27.0