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KVM: x86: Use "is Intel compatible" helper to emulate SYSCALL in !64-bit

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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.

Link: https://lore.kernel.org/r/20240405235603.1173076-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-04-05 16:55:59 -07:00
parent c092fc879f
commit d99e4cb2ae
3 changed files with 16 additions and 36 deletions
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45
arch/x86/kvm/emulate.c
View File

@ -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);

1
arch/x86/kvm/kvm_emulate.h
View File

@ -223,6 +223,7 @@ 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);

6
arch/x86/kvm/x86.c
View File

@ -8549,6 +8549,11 @@ 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);
@ -8647,6 +8652,7 @@ 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,