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KVM: x86: Suppress code #DBs on Intel if MOV/POP SS blocking is active

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Suppress code breakpoints if MOV/POP SS blocking is active and the guest
CPU is Intel, i.e. if the guest thinks it's running on an Intel CPU.
Intel CPUs inhibit code #DBs when MOV/POP SS blocking is active, whereas
AMD (and its descendents) do not.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220830231614.3580124-6-seanjc@google.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-08-30 23:15:52 +00:00 • committed by Paolo Bonzini
parent d500e1ed3d
commit baf67ca8e5
1 changed files with 18 additions and 1 deletions
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19
arch/x86/kvm/x86.c
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@ -8554,6 +8554,23 @@ int kvm_skip_emulated_instruction(struct kvm_vcpu *vcpu)
} }
EXPORT_SYMBOL_GPL(kvm_skip_emulated_instruction); EXPORT_SYMBOL_GPL(kvm_skip_emulated_instruction);
static bool kvm_is_code_breakpoint_inhibited(struct kvm_vcpu *vcpu)
{
u32 shadow;
if (kvm_get_rflags(vcpu) & X86_EFLAGS_RF)
return true;
/*
* Intel CPUs inhibit code #DBs when MOV/POP SS blocking is active,
* but AMD CPUs do not. MOV/POP SS blocking is rare, check that first
* to avoid the relatively expensive CPUID lookup.
*/
shadow = static_call(kvm_x86_get_interrupt_shadow)(vcpu);
return (shadow & KVM_X86_SHADOW_INT_MOV_SS) &&
guest_cpuid_is_intel(vcpu);
}
static bool kvm_vcpu_check_code_breakpoint(struct kvm_vcpu *vcpu, static bool kvm_vcpu_check_code_breakpoint(struct kvm_vcpu *vcpu,
int emulation_type, int *r) int emulation_type, int *r)
{ {
@ -8596,7 +8613,7 @@ static bool kvm_vcpu_check_code_breakpoint(struct kvm_vcpu *vcpu,
} }
if (unlikely(vcpu->arch.dr7 & DR7_BP_EN_MASK) && if (unlikely(vcpu->arch.dr7 & DR7_BP_EN_MASK) &&
!(kvm_get_rflags(vcpu) & X86_EFLAGS_RF)) { !kvm_is_code_breakpoint_inhibited(vcpu)) {
unsigned long eip = kvm_get_linear_rip(vcpu); unsigned long eip = kvm_get_linear_rip(vcpu);
u32 dr6 = kvm_vcpu_check_hw_bp(eip, 0, u32 dr6 = kvm_vcpu_check_hw_bp(eip, 0,
vcpu->arch.dr7, vcpu->arch.dr7,