Commit baf67ca8 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

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



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: default avatarSean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220830231614.3580124-6-seanjc@google.com


Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent d500e1ed

arch/x86/kvm/x86.c

+18 −1
Original line number Diff line number Diff line
@@ -8554,6 +8554,23 @@ int kvm_skip_emulated_instruction(struct kvm_vcpu *vcpu) 
}

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,

					   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) &&

	    !(kvm_get_rflags(vcpu) & X86_EFLAGS_RF)) {

	    !kvm_is_code_breakpoint_inhibited(vcpu)) {

		unsigned long eip = kvm_get_linear_rip(vcpu);

		u32 dr6 = kvm_vcpu_check_hw_bp(eip, 0,

					   vcpu->arch.dr7,