From 5492830370171b6a4ede8a3bfba687a8d0f25fa5 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 10 Jul 2015 13:32:13 +0200 Subject: [PATCH] KVM: svm: handle KVM_X86_QUIRK_CD_NW_CLEARED in svm_get_mt_mask We can disable CD unconditionally when there is no assigned device. KVM now forces guest PAT to all-writeback in that case, so it makes sense to also force CR0.CD=0. When there are assigned devices, emulate cache-disabled operation through the page tables. This behavior is consistent with VMX microcode, where CD/NW are not touched by vmentry/vmexit. However, keep this dependent on the quirk because OVMF enables the caches too late. Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 8e0c0844c6b9..d1a114d8d22b 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1173,6 +1173,10 @@ static u64 svm_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio) if (!is_mmio && !kvm_arch_has_assigned_device(vcpu->kvm)) return 0; + if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED) && + kvm_read_cr0(vcpu) & X86_CR0_CD) + return _PAGE_NOCACHE; + mtrr = kvm_mtrr_get_guest_memory_type(vcpu, gfn); return mtrr2protval[mtrr]; } @@ -1667,13 +1671,10 @@ static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) if (!vcpu->fpu_active) cr0 |= X86_CR0_TS; - /* - * re-enable caching here because the QEMU bios - * does not do it - this results in some delay at - * reboot - */ - if (kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED)) - cr0 &= ~(X86_CR0_CD | X86_CR0_NW); + + /* These are emulated via page tables. */ + cr0 &= ~(X86_CR0_CD | X86_CR0_NW); + svm->vmcb->save.cr0 = cr0; mark_dirty(svm->vmcb, VMCB_CR); update_cr0_intercept(svm); -- 2.20.1