From a09020ea2e2e645b95ed603e075938d413f1114f Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Fri, 12 Oct 2018 07:58:38 +0100 Subject: [PATCH 08/17] intel-iommu: send PSI always even if across PDEs RH-Author: Peter Xu Message-id: <20181012075846.25449-2-peterx@redhat.com> Patchwork-id: 82674 O-Subject: [RHEL-8 qemu-kvm PATCH 1/9] intel-iommu: send PSI always even if across PDEs Bugzilla: 1450712 RH-Acked-by: Auger Eric RH-Acked-by: Xiao Wang RH-Acked-by: Michael S. Tsirkin SECURITY IMPLICATION: without this patch, any guest with both assigned device and a vIOMMU might encounter stale IO page mappings even if guest has already unmapped the page, which may lead to guest memory corruption. The stale mappings will only be limited to the guest's own memory range, so it should not affect the host memory or other guests on the host. During IOVA page table walking, there is a special case when the PSI covers one whole PDE (Page Directory Entry, which contains 512 Page Table Entries) or more. In the past, we skip that entry and we don't notify the IOMMU notifiers. This is not correct. We should send UNMAP notification to registered UNMAP notifiers in this case. For UNMAP only notifiers, this might cause IOTLBs cached in the devices even if they were already invalid. For MAP/UNMAP notifiers like vfio-pci, this will cause stale page mappings. This special case doesn't trigger often, but it is very easy to be triggered by nested device assignments, since in that case we'll possibly map the whole L2 guest RAM region into the device's IOVA address space (several GBs at least), which is far bigger than normal kernel driver usages of the device (tens of MBs normally). Without this patch applied to L1 QEMU, nested device assignment to L2 guests will dump some errors like: qemu-system-x86_64: VFIO_MAP_DMA: -17 qemu-system-x86_64: vfio_dma_map(0x557305420c30, 0xad000, 0x1000, 0x7f89a920d000) = -17 (File exists) CC: QEMU Stable Acked-by: Jason Wang [peterx: rewrite the commit message] Signed-off-by: Peter Xu Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin (cherry picked from commit 36d2d52bdb45f5b753a61fdaf0fe7891f1f5b61d) Signed-off-by: Peter Xu Signed-off-by: Danilo C. L. de Paula --- hw/i386/intel_iommu.c | 42 ++++++++++++++++++++++++++++++------------ 1 file changed, 30 insertions(+), 12 deletions(-) diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c index fb31de9..b359efd 100644 --- a/hw/i386/intel_iommu.c +++ b/hw/i386/intel_iommu.c @@ -722,6 +722,15 @@ static int vtd_iova_to_slpte(VTDContextEntry *ce, uint64_t iova, bool is_write, typedef int (*vtd_page_walk_hook)(IOMMUTLBEntry *entry, void *private); +static int vtd_page_walk_one(IOMMUTLBEntry *entry, int level, + vtd_page_walk_hook hook_fn, void *private) +{ + assert(hook_fn); + trace_vtd_page_walk_one(level, entry->iova, entry->translated_addr, + entry->addr_mask, entry->perm); + return hook_fn(entry, private); +} + /** * vtd_page_walk_level - walk over specific level for IOVA range * @@ -781,28 +790,37 @@ static int vtd_page_walk_level(dma_addr_t addr, uint64_t start, */ entry_valid = read_cur | write_cur; + entry.target_as = &address_space_memory; + entry.iova = iova & subpage_mask; + entry.perm = IOMMU_ACCESS_FLAG(read_cur, write_cur); + entry.addr_mask = ~subpage_mask; + if (vtd_is_last_slpte(slpte, level)) { - entry.target_as = &address_space_memory; - entry.iova = iova & subpage_mask; /* NOTE: this is only meaningful if entry_valid == true */ entry.translated_addr = vtd_get_slpte_addr(slpte, aw); - entry.addr_mask = ~subpage_mask; - entry.perm = IOMMU_ACCESS_FLAG(read_cur, write_cur); if (!entry_valid && !notify_unmap) { trace_vtd_page_walk_skip_perm(iova, iova_next); goto next; } - trace_vtd_page_walk_one(level, entry.iova, entry.translated_addr, - entry.addr_mask, entry.perm); - if (hook_fn) { - ret = hook_fn(&entry, private); - if (ret < 0) { - return ret; - } + ret = vtd_page_walk_one(&entry, level, hook_fn, private); + if (ret < 0) { + return ret; } } else { if (!entry_valid) { - trace_vtd_page_walk_skip_perm(iova, iova_next); + if (notify_unmap) { + /* + * The whole entry is invalid; unmap it all. + * Translated address is meaningless, zero it. + */ + entry.translated_addr = 0x0; + ret = vtd_page_walk_one(&entry, level, hook_fn, private); + if (ret < 0) { + return ret; + } + } else { + trace_vtd_page_walk_skip_perm(iova, iova_next); + } goto next; } ret = vtd_page_walk_level(vtd_get_slpte_addr(slpte, aw), iova, -- 1.8.3.1