From: Jan Beulich Date: Fri, 23 Oct 2020 08:06:53 +0000 (+0200) Subject: IOMMU/EPT: avoid double flushing in shared page table case X-Git-Tag: archive/raspbian/4.16.0+51-g0941d6cb-1+rpi1~2^2~42^2~1478 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=83432adeb82122e392a3bfc2a8818d25ca9e69ed;p=xen.git 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 --- 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;