From bc7cde94e2b5364f56e7d4c6f257980023c7aae0 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 22 Jun 2021 10:56:50 -0700 Subject: [PATCH] Revert "KVM: x86/mmu: Drop kvm_mmu_extended_role.cr4_la57 hack" Restore CR4.LA57 to the mmu_role to fix an amusing edge case with nested virtualization. When KVM (L0) is using TDP, CR4.LA57 is not reflected in mmu_role.base.level because that tracks the shadow root level, i.e. TDP level. Normally, this is not an issue because LA57 can't be toggled while long mode is active, i.e. the guest has to first disable paging, then toggle LA57, then re-enable paging, thus ensuring an MMU reinitialization. But if L1 is crafty, it can load a new CR4 on VM-Exit and toggle LA57 without having to bounce through an unpaged section. L1 can also load a new CR3 on exit, i.e. it doesn't even need to play crazy paging games, a single entry PML5 is sufficient. Such shenanigans are only problematic if L0 and L1 use TDP, otherwise L1 and L2 share an MMU that gets reinitialized on nested VM-Enter/VM-Exit due to mmu_role.base.guest_mode. Note, in the L2 case with nested TDP, even though L1 can switch between L2s with different LA57 settings, thus bypassing the paging requirement, in that case KVM's nested_mmu will track LA57 in base.level. This reverts commit 9906442b85c024015e728ef5d7f5ea7f4d846878. Fixes: 9906442b85c0 ("KVM: x86/mmu: Drop kvm_mmu_extended_role.cr4_la57 hack") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-Id: <20210622175739.3610207-6-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/mmu/mmu.c | 1 + 2 files changed, 2 insertions(+) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 408051552121a..a474cd13b0c84 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -320,6 +320,7 @@ union kvm_mmu_extended_role { unsigned int cr4_pke:1; unsigned int cr4_smap:1; unsigned int cr4_smep:1; + unsigned int cr4_la57:1; unsigned int maxphyaddr:6; }; }; diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 444e068e6ad99..fa35762f325c4 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4537,6 +4537,7 @@ static union kvm_mmu_extended_role kvm_calc_mmu_role_ext(struct kvm_vcpu *vcpu) ext.cr4_smap = !!kvm_read_cr4_bits(vcpu, X86_CR4_SMAP); ext.cr4_pse = !!is_pse(vcpu); ext.cr4_pke = !!kvm_read_cr4_bits(vcpu, X86_CR4_PKE); + ext.cr4_la57 = !!kvm_read_cr4_bits(vcpu, X86_CR4_LA57); ext.maxphyaddr = cpuid_maxphyaddr(vcpu); ext.valid = 1; -- 2.39.5