Commit c092fc87 authored by Sean Christopherson's avatar Sean Christopherson

KVM: x86: Inhibit code #DBs in MOV-SS shadow for all Intel compat vCPUs

Treat code #DBs as inhibited in MOV/POP-SS shadows for vCPU models that
are Intel compatible, not just strictly vCPUs with vendor==Intel.  The
behavior is explicitly called out in the SDM, and thus architectural, i.e.
applies to all CPUs that implement Intel's architecture, and isn't a quirk
that is unique to CPUs manufactured by Intel:

  However, if an instruction breakpoint is placed on an instruction located
  immediately after a POP SS/MOV SS instruction, the breakpoint will be
  suppressed as if EFLAGS.RF were 1.

Applying the behavior strictly to Intel wasn't intentional, KVM simply
didn't have a concept of "Intel compatible" as of commit baf67ca8
("KVM: x86: Suppress code #DBs on Intel if MOV/POP SS blocking is active").

Link: https://lore.kernel.org/r/20240405235603.1173076-6-seanjc@google.comSigned-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 6463e5e4
...@@ -9028,19 +9028,17 @@ EXPORT_SYMBOL_GPL(kvm_skip_emulated_instruction); ...@@ -9028,19 +9028,17 @@ EXPORT_SYMBOL_GPL(kvm_skip_emulated_instruction);
static bool kvm_is_code_breakpoint_inhibited(struct kvm_vcpu *vcpu) static bool kvm_is_code_breakpoint_inhibited(struct kvm_vcpu *vcpu)
{ {
u32 shadow;
if (kvm_get_rflags(vcpu) & X86_EFLAGS_RF) if (kvm_get_rflags(vcpu) & X86_EFLAGS_RF)
return true; return true;
/* /*
* Intel CPUs inhibit code #DBs when MOV/POP SS blocking is active, * Intel compatible CPUs inhibit code #DBs when MOV/POP SS blocking is
* but AMD CPUs do not. MOV/POP SS blocking is rare, check that first * active, but AMD compatible CPUs do not.
* to avoid the relatively expensive CPUID lookup.
*/ */
shadow = static_call(kvm_x86_get_interrupt_shadow)(vcpu); if (!guest_cpuid_is_intel_compatible(vcpu))
return (shadow & KVM_X86_SHADOW_INT_MOV_SS) && return false;
guest_cpuid_is_intel(vcpu);
return static_call(kvm_x86_get_interrupt_shadow)(vcpu) & KVM_X86_SHADOW_INT_MOV_SS;
} }
static bool kvm_vcpu_check_code_breakpoint(struct kvm_vcpu *vcpu, static bool kvm_vcpu_check_code_breakpoint(struct kvm_vcpu *vcpu,
......
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