From 452d62227958e149e5c7b0084a559c0957c3ff2a Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Mon, 13 Jul 2020 15:15:14 +0100 Subject: [PATCH 1/2] KVM: arm64: Restore missing ISB on nVHE __tlb_switch_to_guest Commit a0e50aa3f4a8 ("KVM: arm64: Factor out stage 2 page table data from struct kvm") dropped the ISB after __load_guest_stage2(), only leaving the one that is required when the speculative AT workaround is in effect. As Andrew points it: "This alternative is 'backwards' to avoid a double ISB as there is one in __load_guest_stage2 when the workaround is active." Restore the missing ISB, conditionned on the AT workaround not being active. Fixes: a0e50aa3f4a8 ("KVM: arm64: Factor out stage 2 page table data from struct kvm") Reported-by: Andrew Scull Reported-by: Thomas Tai Signed-off-by: Marc Zyngier --- arch/arm64/kvm/hyp/nvhe/tlb.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/arm64/kvm/hyp/nvhe/tlb.c b/arch/arm64/kvm/hyp/nvhe/tlb.c index 69eae608d670..b15d65a42042 100644 --- a/arch/arm64/kvm/hyp/nvhe/tlb.c +++ b/arch/arm64/kvm/hyp/nvhe/tlb.c @@ -31,7 +31,14 @@ static void __tlb_switch_to_guest(struct kvm_s2_mmu *mmu, isb(); } + /* + * __load_guest_stage2() includes an ISB only when the AT + * workaround is applied. Take care of the opposite condition, + * ensuring that we always have an ISB, but not two ISBs back + * to back. + */ __load_guest_stage2(mmu); + asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)); } static void __tlb_switch_to_host(struct tlb_inv_context *cxt) From b502e6ecdc3b6d381bd72c5f879bc1e00d6fe7db Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 29 Sep 2020 08:31:32 -0400 Subject: [PATCH 2/2] KVM: VMX: update PFEC_MASK/PFEC_MATCH together with PF intercept The PFEC_MASK and PFEC_MATCH fields in the VMCS reverse the meaning of the #PF intercept bit in the exception bitmap when they do not match. This means that, if PFEC_MASK and/or PFEC_MATCH are set, the hypervisor can get a vmexit for #PF exceptions even when the corresponding bit is clear in the exception bitmap. This is unexpected and is promptly detected by a WARN_ON_ONCE. To fix it, reset PFEC_MASK and PFEC_MATCH when the #PF intercept is disabled (as is common with enable_ept && !allow_smaller_maxphyaddr). Reported-by: Qian Cai > Reported-by: Naresh Kamboju Tested-by: Naresh Kamboju Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/vmx.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index f0384e93548a..f4e9c310032a 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -794,6 +794,18 @@ void update_exception_bitmap(struct kvm_vcpu *vcpu) */ if (is_guest_mode(vcpu)) eb |= get_vmcs12(vcpu)->exception_bitmap; + else { + /* + * If EPT is enabled, #PF is only trapped if MAXPHYADDR is mismatched + * between guest and host. In that case we only care about present + * faults. For vmcs02, however, PFEC_MASK and PFEC_MATCH are set in + * prepare_vmcs02_rare. + */ + bool selective_pf_trap = enable_ept && (eb & (1u << PF_VECTOR)); + int mask = selective_pf_trap ? PFERR_PRESENT_MASK : 0; + vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, mask); + vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, mask); + } vmcs_write32(EXCEPTION_BITMAP, eb); } @@ -4355,16 +4367,6 @@ static void init_vmcs(struct vcpu_vmx *vmx) vmx->pt_desc.guest.output_mask = 0x7F; vmcs_write64(GUEST_IA32_RTIT_CTL, 0); } - - /* - * If EPT is enabled, #PF is only trapped if MAXPHYADDR is mismatched - * between guest and host. In that case we only care about present - * faults. - */ - if (enable_ept) { - vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, PFERR_PRESENT_MASK); - vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, PFERR_PRESENT_MASK); - } } static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)