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KVM: x86: Read CR4.DE in emulator if and only if accessing DR4 or DR5

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Micro-optimize emulation of MOV DR instructions by checking CR4.DE if and
only if DR4 or DR5 is being accessed.

No functional change intended.

Reviewed-by: Jim Mattson <jmattson@google.com>
Link: https://patch.msgid.link/20260612230113.684301-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2026-06-12 16:01:13 -07:00
parent b077cfed52
commit 7a642d8dcf
1 changed files with 1 additions and 3 deletions
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4
arch/x86/kvm/emulate.c
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@ -3840,13 +3840,11 @@ static int check_dr_read(struct x86_emulate_ctxt *ctxt)
{
bool is_intel = ctxt->ops->guest_cpuid_is_intel_compatible(ctxt);
int dr = ctxt->modrm_reg;
u64 cr4;
if (dr > 7)
return emulate_ud(ctxt);
cr4 = ctxt->ops->get_cr(ctxt, 4);
if ((cr4 & X86_CR4_DE) && (dr == 4 || dr == 5))
if ((dr == 4 || dr == 5) && (ctxt->ops->get_cr(ctxt, 4) & X86_CR4_DE))
return emulate_ud(ctxt);
/* Intel CPUs prioritize the DR7.GD=1 #DB over the CPL>0 #GP. */