This is a note to let you know that I've just added the patch titled Revert "KVM: x86: apply guest MTRR virtualization on host reserved pages" to the 4.2-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: revert-kvm-x86-apply-guest-mtrr-virtualization-on-host-reserved-pages.patch and it can be found in the queue-4.2 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 606decd67049217684e3cb5a54104d51ddd4ef35 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini <pbonzini@xxxxxxxxxx> Date: Thu, 1 Oct 2015 13:12:47 +0200 Subject: Revert "KVM: x86: apply guest MTRR virtualization on host reserved pages" From: Paolo Bonzini <pbonzini@xxxxxxxxxx> commit 606decd67049217684e3cb5a54104d51ddd4ef35 upstream. This reverts commit fd717f11015f673487ffc826e59b2bad69d20fe5. It was reported to cause Machine Check Exceptions (bug 104091). Reported-by: harn-solo@xxxxxx Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kvm/svm.c | 7 +++++-- arch/x86/kvm/vmx.c | 11 ++++++++--- 2 files changed, 13 insertions(+), 5 deletions(-) --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1166,11 +1166,14 @@ static u64 svm_get_mt_mask(struct kvm_vc u8 mtrr; /* - * 1. MMIO: trust guest MTRR, so same as item 3. + * 1. MMIO: always map as UC * 2. No passthrough: always map as WB, and force guest PAT to WB as well * 3. Passthrough: can't guarantee the result, try to trust guest. */ - if (!is_mmio && !kvm_arch_has_assigned_device(vcpu->kvm)) + if (is_mmio) + return _PAGE_NOCACHE; + + if (!kvm_arch_has_assigned_device(vcpu->kvm)) return 0; mtrr = kvm_mtrr_get_guest_memory_type(vcpu, gfn); --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -8634,17 +8634,22 @@ static u64 vmx_get_mt_mask(struct kvm_vc u64 ipat = 0; /* For VT-d and EPT combination - * 1. MMIO: guest may want to apply WC, trust it. + * 1. MMIO: always map as UC * 2. EPT with VT-d: * a. VT-d without snooping control feature: can't guarantee the - * result, try to trust guest. So the same as item 1. + * result, try to trust guest. * b. VT-d with snooping control feature: snooping control feature of * VT-d engine can guarantee the cache correctness. Just set it * to WB to keep consistent with host. So the same as item 3. * 3. EPT without VT-d: always map as WB and set IPAT=1 to keep * consistent with host MTRR */ - if (!is_mmio && !kvm_arch_has_noncoherent_dma(vcpu->kvm)) { + if (is_mmio) { + cache = MTRR_TYPE_UNCACHABLE; + goto exit; + } + + if (!kvm_arch_has_noncoherent_dma(vcpu->kvm)) { ipat = VMX_EPT_IPAT_BIT; cache = MTRR_TYPE_WRBACK; goto exit; Patches currently in stable-queue which might be from pbonzini@xxxxxxxxxx are queue-4.2/kvm-fix-double-free-for-fast-mmio-eventfd.patch queue-4.2/kvm-fix-zero-length-mmio-searching.patch queue-4.2/revert-kvm-x86-apply-guest-mtrr-virtualization-on-host-reserved-pages.patch queue-4.2/kvm-vmx-fix-vpid-is-0000h-in-non-root-operation.patch queue-4.2/revert-kvm-svm-use-npt-page-attributes.patch queue-4.2/revert-kvm-svm-sync-g_pat-with-guest-written-pat-value.patch queue-4.2/kvm-factor-out-core-eventfd-assign-deassign-logic.patch queue-4.2/kvm-x86-trap-amd-msrs-for-the-tseg-base-and-mask.patch queue-4.2/kvm-svm-reset-mmu-on-vcpu-reset.patch queue-4.2/kvm-don-t-try-to-register-to-kvm_fast_mmio_bus-for-non-mmio-eventfd.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html