From 83432adeb82122e392a3bfc2a8818d25ca9e69ed Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 23 Oct 2020 10:06:53 +0200 Subject: [PATCH] IOMMU/EPT: avoid double flushing in shared page table case While the flush coalescing optimization has been helping the non-shared case, it has actually lead to double flushes in the shared case (which ought to be the more common one nowadays at least): Once from *_set_entry() and a second time up the call tree from wherever the overriding flag gets played with. In alignment with XSA-346 suppress flushing in this case. Similarly avoid excessive setting of IOMMU_FLUSHF_added on the batched flushes: "idx" hasn't been added a new mapping for. Signed-off-by: Jan Beulich Reviewed-by: Kevin Tian --- xen/arch/x86/mm/p2m-ept.c | 2 +- xen/common/memory.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c index 12cf38f6eb..476458b1e0 100644 --- a/xen/arch/x86/mm/p2m-ept.c +++ b/xen/arch/x86/mm/p2m-ept.c @@ -842,7 +842,7 @@ out: if ( rc == 0 && p2m_is_hostp2m(p2m) && need_modify_vtd_table ) { - if ( iommu_use_hap_pt(d) ) + if ( iommu_use_hap_pt(d) && !this_cpu(iommu_dont_flush_iotlb) ) rc = iommu_iotlb_flush(d, _dfn(gfn), 1ul << order, (iommu_flags ? IOMMU_FLUSHF_added : 0) | (vtd_pte_present ? IOMMU_FLUSHF_modified diff --git a/xen/common/memory.c b/xen/common/memory.c index 7075e233aa..df85b550a1 100644 --- a/xen/common/memory.c +++ b/xen/common/memory.c @@ -870,7 +870,7 @@ int xenmem_add_to_physmap(struct domain *d, struct xen_add_to_physmap *xatp, this_cpu(iommu_dont_flush_iotlb) = 0; ret = iommu_iotlb_flush(d, _dfn(xatp->idx - done), done, - IOMMU_FLUSHF_added | IOMMU_FLUSHF_modified); + IOMMU_FLUSHF_modified); if ( unlikely(ret) && rc >= 0 ) rc = ret; -- 2.39.5