From b9d44f9091ac6c325fc2f7b7671b462fb36abbed Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 30 Aug 2022 23:15:54 +0000 Subject: [PATCH] KVM: nVMX: Prioritize TSS T-flag #DBs over Monitor Trap Flag Service TSS T-flag #DBs prior to pending MTFs, as such #DBs are higher priority than MTF. KVM itself doesn't emulate TSS #DBs, and any such exceptions injected from L1 will be handled by hardware (or morphed to a fault-like exception if injection fails), but theoretically userspace could pend a TSS T-flag #DB in conjunction with a pending MTF. Note, there's no known use case this fixes, it's purely to be technically correct with respect to Intel's SDM. Cc: Oliver Upton Cc: Peter Shier Fixes: 5ef8acbdd687 ("KVM: nVMX: Emulate MTF when performing instruction emulation") Signed-off-by: Sean Christopherson Reviewed-by: Maxim Levitsky Link: https://lore.kernel.org/r/20220830231614.3580124-8-seanjc@google.com Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/nested.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 9e25e75..60e6a26 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -3985,15 +3985,17 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu) } /* - * Process any exceptions that are not debug traps before MTF. + * Process exceptions that are higher priority than Monitor Trap Flag: + * fault-like exceptions, TSS T flag #DB (not emulated by KVM, but + * could theoretically come in from userspace), and ICEBP (INT1). * * Note that only a pending nested run can block a pending exception. * Otherwise an injected NMI/interrupt should either be * lost or delivered to the nested hypervisor in the IDT_VECTORING_INFO, * while delivering the pending exception. */ - - if (vcpu->arch.exception.pending && !vmx_get_pending_dbg_trap(vcpu)) { + if (vcpu->arch.exception.pending && + !(vmx_get_pending_dbg_trap(vcpu) & ~DR6_BT)) { if (vmx->nested.nested_run_pending) return -EBUSY; if (!nested_vmx_check_exception(vcpu, &exit_qual)) -- 2.7.4