From ec7771ab471ba6a945350353617e2e3385d0e013 Mon Sep 17 00:00:00 2001 From: Mohammed Gamal Date: Fri, 10 Jul 2020 17:48:05 +0200 Subject: [PATCH] KVM: x86: mmu: Add guest physical address check in translate_gpa() Intel processors of various generations have supported 36, 39, 46 or 52 bits for physical addresses. Until IceLake introduced MAXPHYADDR==52, running on a machine with higher MAXPHYADDR than the guest more or less worked, because software that relied on reserved address bits (like KVM) generally used bit 51 as a marker and therefore the page faults where generated anyway. Unfortunately this is not true anymore if the host MAXPHYADDR is 52, and this can cause problems when migrating from a MAXPHYADDR<52 machine to one with MAXPHYADDR==52. Typically, the latter are machines that support 5-level page tables, so they can be identified easily from the LA57 CPUID bit. When that happens, the guest might have a physical address with reserved bits set, but the host won't see that and trap it. Hence, we need to check page faults' physical addresses against the guest's maximum physical memory and if it's exceeded, we need to add the PFERR_RSVD_MASK bits to the page fault error code. This patch does this for the MMU's page walks. The next patches will ensure that the correct exception and error code is produced whenever no host-reserved bits are set in page table entries. Signed-off-by: Mohammed Gamal Signed-off-by: Paolo Bonzini Message-Id: <20200710154811.418214-4-mgamal@redhat.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/mmu.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 01e7277acb48..77810ce66bdb 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -519,6 +519,12 @@ static bool check_mmio_spte(struct kvm_vcpu *vcpu, u64 spte) static gpa_t translate_gpa(struct kvm_vcpu *vcpu, gpa_t gpa, u32 access, struct x86_exception *exception) { + /* Check if guest physical address doesn't exceed guest maximum */ + if (kvm_mmu_is_illegal_gpa(vcpu, gpa)) { + exception->error_code |= PFERR_RSVD_MASK; + return UNMAPPED_GVA; + } + return gpa; }