linux-kernel - [PATCH 09/10] KVM: x86: Open code vendor_intel() in string_registers

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Date: Fri,  5 Apr 2024 16:56:02 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Sandipan Das <sandipan.das@....com>, Jim Mattson <jmattson@...gle.com>, 
	Like Xu <like.xu.linux@...il.com>
Subject: [PATCH 09/10] KVM: x86: Open code vendor_intel() in string_registers_quirk()

Open code the is_guest_vendor_intel() check in string_registers_quirk() to
discourage makiking exact vendor==Intel checks in the emulator, and to
remove the rather awful #ifdeffery.

The string quirk is literally the only Intel specific, *non-architectural*
behavior that KVM emulates.  All Intel specific behavior that is
architecturally defined applies to all vendors that are compatible with
Intel's architecture, i.e. should use guest_cpuid_is_intel_compatible().

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/emulate.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 26e8c197a1d1..1acd97c6fa53 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2354,17 +2354,6 @@ setup_syscalls_segments(struct desc_struct *cs, struct desc_struct *ss)
 	ss->avl = 0;
 }
 
-#ifdef CONFIG_X86_64
-static bool vendor_intel(struct x86_emulate_ctxt *ctxt)
-{
-	u32 eax, ebx, ecx, edx;
-
-	eax = ecx = 0;
-	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, true);
-	return is_guest_vendor_intel(ebx, ecx, edx);
-}
-#endif
-
 static int em_syscall(struct x86_emulate_ctxt *ctxt)
 {
 	const struct x86_emulate_ops *ops = ctxt->ops;
@@ -2622,7 +2611,14 @@ static void string_registers_quirk(struct x86_emulate_ctxt *ctxt)
 	 * manner when ECX is zero due to REP-string optimizations.
 	 */
 #ifdef CONFIG_X86_64
-	if (ctxt->ad_bytes != 4 || !vendor_intel(ctxt))
+	u32 eax, ebx, ecx, edx;
+
+	if (ctxt->ad_bytes != 4)
+		return;
+
+	eax = ecx = 0;
+	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, true);
+	if (!is_guest_vendor_intel(ebx, ecx, edx))
 		return;
 
 	*reg_write(ctxt, VCPU_REGS_RCX) = 0;
-- 
2.44.0.478.gd926399ef9-goog