From: Zhenzhong Duan Date: Thu, 15 Jun 2023 03:26:24 +0000 (+0800) Subject: intel_iommu: Fix a potential issue in VFIO dirty page sync X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=e80c1e4c7d057fe5c96db588e651b934757a912e;p=qemu.git intel_iommu: Fix a potential issue in VFIO dirty page sync Peter Xu found a potential issue: "The other thing is when I am looking at the new code I found that we actually extended the replay() to be used also in dirty tracking of vfio, in vfio_sync_dirty_bitmap(). For that maybe it's already broken if unmap_all() because afaiu log_sync() can be called in migration thread anytime during DMA so I think it means the device is prone to DMA with the IOMMU pgtable quickly erased and rebuilt here, which means the DMA could fail unexpectedly. Copy Alex, Kirti and Neo." Fix it by replacing the unmap_all() to only evacuate the iova tree (keeping all host mappings untouched, IOW, don't notify UNMAP), and do a full resync in page walk which will notify all existing mappings as MAP. This way we don't interrupt with any existing mapping if there is (e.g. for the dirty sync case), meanwhile we keep sync too to latest (for moving a vfio device into an existing iommu group). Suggested-by: Peter Xu Signed-off-by: Zhenzhong Duan Reviewed-by: Peter Xu Message-Id: <20230615032626.314476-2-zhenzhong.duan@intel.com> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c index 94d52f4205..34af12f392 100644 --- a/hw/i386/intel_iommu.c +++ b/hw/i386/intel_iommu.c @@ -3825,13 +3825,10 @@ static void vtd_iommu_replay(IOMMUMemoryRegion *iommu_mr, IOMMUNotifier *n) IntelIOMMUState *s = vtd_as->iommu_state; uint8_t bus_n = pci_bus_num(vtd_as->bus); VTDContextEntry ce; + DMAMap map = { .iova = 0, .size = HWADDR_MAX }; - /* - * The replay can be triggered by either a invalidation or a newly - * created entry. No matter what, we release existing mappings - * (it means flushing caches for UNMAP-only registers). - */ - vtd_address_space_unmap(vtd_as, n); + /* replay is protected by BQL, page walk will re-setup it safely */ + iova_tree_remove(vtd_as->iova_tree, map); if (vtd_dev_to_context_entry(s, bus_n, vtd_as->devfn, &ce) == 0) { trace_vtd_replay_ce_valid(s->root_scalable ? "scalable mode" :