Use guest_cpuid_is_intel_compatible() to determine whether SYSCALL in
32-bit Protected Mode (including Compatibility Mode) should #UD or succeed.
The existing code already does the exact equivalent of
guest_cpuid_is_intel_compatible(), just in a rather roundabout way.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 45 ++++++++------------------------------
arch/x86/kvm/kvm_emulate.h | 1 +
arch/x86/kvm/x86.c | 6 +++++
3 files changed, 16 insertions(+), 36 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 5d4c86133453..1fb73d96bdf0 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2363,41 +2363,6 @@ static bool vendor_intel(struct x86_emulate_ctxt *ctxt)
return is_guest_vendor_intel(ebx, ecx, edx);
}
-static bool em_syscall_is_enabled(struct x86_emulate_ctxt *ctxt)
-{
- const struct x86_emulate_ops *ops = ctxt->ops;
- u32 eax, ebx, ecx, edx;
-
- /*
- * syscall should always be enabled in longmode - so only become
- * vendor specific (cpuid) if other modes are active...
- */
- if (ctxt->mode == X86EMUL_MODE_PROT64)
- return true;
-
- eax = 0x00000000;
- ecx = 0x00000000;
- ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, true);
- /*
- * remark: Intel CPUs only support "syscall" in 64bit longmode. Also a
- * 64bit guest with a 32bit compat-app running will #UD !! While this
- * behaviour can be fixed (by emulating) into AMD response - CPUs of
- * AMD can't behave like Intel.
- */
- if (is_guest_vendor_intel(ebx, ecx, edx))
- return false;
-
- if (is_guest_vendor_amd(ebx, ecx, edx) ||
- is_guest_vendor_hygon(ebx, ecx, edx))
- return true;
-
- /*
- * default: (not Intel, not AMD, not Hygon), apply Intel's
- * stricter rules...
- */
- return false;
-}
-
static int em_syscall(struct x86_emulate_ctxt *ctxt)
{
const struct x86_emulate_ops *ops = ctxt->ops;
@@ -2411,7 +2376,15 @@ static int em_syscall(struct x86_emulate_ctxt *ctxt)
ctxt->mode == X86EMUL_MODE_VM86)
return emulate_ud(ctxt);
- if (!(em_syscall_is_enabled(ctxt)))
+ /*
+ * Intel compatible CPUs only support SYSCALL in 64-bit mode, whereas
+ * AMD allows SYSCALL in any flavor of protected mode. Note, it's
+ * infeasible to emulate Intel behavior when running on AMD hardware,
+ * as SYSCALL won't fault in the "wrong" mode, i.e. there is no #UD
+ * for KVM to trap-and-emulate, unlike emulating AMD on Intel.
+ */
+ if (ctxt->mode != X86EMUL_MODE_PROT64 &&
+ ctxt->ops->guest_cpuid_is_intel_compatible(ctxt))
return emulate_ud(ctxt);
ops->get_msr(ctxt, MSR_EFER, &efer);
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 5382646162a3..0f71d4699b78 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -222,6 +222,7 @@ struct x86_emulate_ops {
bool (*guest_has_movbe)(struct x86_emulate_ctxt *ctxt);
bool (*guest_has_fxsr)(struct x86_emulate_ctxt *ctxt);
bool (*guest_has_rdpid)(struct x86_emulate_ctxt *ctxt);
+ bool (*guest_cpuid_is_intel_compatible)(struct x86_emulate_ctxt *ctxt);
void (*set_nmi_mask)(struct x86_emulate_ctxt *ctxt, bool masked);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8ea6f4fc910f..ac607b41890e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8505,6 +8505,11 @@ static bool emulator_guest_has_rdpid(struct x86_emulate_ctxt *ctxt)
return guest_cpuid_has(emul_to_vcpu(ctxt), X86_FEATURE_RDPID);
}
+static bool emulator_guest_cpuid_is_intel_compatible(struct x86_emulate_ctxt *ctxt)
+{
+ return guest_cpuid_is_intel_compatible(emul_to_vcpu(ctxt));
+}
+
static ulong emulator_read_gpr(struct x86_emulate_ctxt *ctxt, unsigned reg)
{
return kvm_register_read_raw(emul_to_vcpu(ctxt), reg);
@@ -8603,6 +8608,7 @@ static const struct x86_emulate_ops emulate_ops = {
.guest_has_movbe = emulator_guest_has_movbe,
.guest_has_fxsr = emulator_guest_has_fxsr,
.guest_has_rdpid = emulator_guest_has_rdpid,
+ .guest_cpuid_is_intel_compatible = emulator_guest_cpuid_is_intel_compatible,
.set_nmi_mask = emulator_set_nmi_mask,
.is_smm = emulator_is_smm,
.is_guest_mode = emulator_is_guest_mode,
--
2.44.0.478.gd926399ef9-goog
