Commit 4067c239 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: x86: Allow SYSENTER in Compatibility Mode for all Intel compat vCPUs 

Emulate SYSENTER in Compatibility Mode for all vCPUs models that are
compatible with Intel's architecture, as the behavior if SYSENTER is
architecturally defined in Intel's SDM, i.e. should be followed by any
CPU that implements Intel's architecture.

Link: https://lore.kernel.org/r/20240405235603.1173076-9-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent dc2b8b2b

arch/x86/kvm/emulate.c

+6 −4
Original line number Diff line number Diff line
@@ -2354,6 +2354,7 @@ 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;
@@ -2362,6 +2363,7 @@ static bool vendor_intel(struct x86_emulate_ctxt *ctxt) 
	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)

{
@@ -2444,11 +2446,11 @@ static int em_sysenter(struct x86_emulate_ctxt *ctxt) 
		return emulate_gp(ctxt, 0);



	/*

	 * Not recognized on AMD in compat mode (but is recognized in legacy

	 * mode).

	 * Intel's architecture allows SYSENTER in compatibility mode, but AMD

	 * does not.  Note, AMD does allow SYSENTER in legacy protected mode.

	 */

	if ((ctxt->mode != X86EMUL_MODE_PROT64) && (efer & EFER_LMA)

	    && !vendor_intel(ctxt))

	if ((ctxt->mode != X86EMUL_MODE_PROT64) && (efer & EFER_LMA) &&

	    !ctxt->ops->guest_cpuid_is_intel_compatible(ctxt))

		return emulate_ud(ctxt);



	/* sysenter/sysexit have not been tested in 64bit mode. */