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Subject[PATCH v2 1/5] KVM: x86: Add dedicated emulator helpers for querying CPUID features
Date
Add feature-specific helpers for querying guest CPUID support from the
emulator instead of having the emulator do a full CPUID and perform its
own bit tests. The primary motivation is to eliminate the emulator's
usage of bit() so that future patches can add more extensive build-time
assertions on the usage of bit() without having to expose yet more code
to the emulator.

Note, providing a generic guest_cpuid_has() to the emulator doesn't work
due to the existing built-time assertions in guest_cpuid_has(), which
require the feature being checked to be a compile-time constant.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/include/asm/kvm_emulate.h | 4 ++++
arch/x86/kvm/emulate.c | 21 +++------------------
arch/x86/kvm/x86.c | 18 ++++++++++++++++++
3 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 77cf6c11f66b..03946eb3e2b9 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -222,6 +222,10 @@ struct x86_emulate_ops {

bool (*get_cpuid)(struct x86_emulate_ctxt *ctxt, u32 *eax, u32 *ebx,
u32 *ecx, u32 *edx, bool check_limit);
+ bool (*guest_has_long_mode)(struct x86_emulate_ctxt *ctxt);
+ bool (*guest_has_movbe)(struct x86_emulate_ctxt *ctxt);
+ bool (*guest_has_fxsr)(struct x86_emulate_ctxt *ctxt);
+
void (*set_nmi_mask)(struct x86_emulate_ctxt *ctxt, bool masked);

unsigned (*get_hflags)(struct x86_emulate_ctxt *ctxt);
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 952d1a4f4d7e..e9833e345a5c 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2348,12 +2348,7 @@ static int em_lseg(struct x86_emulate_ctxt *ctxt)
static int emulator_has_longmode(struct x86_emulate_ctxt *ctxt)
{
#ifdef CONFIG_X86_64
- u32 eax, ebx, ecx, edx;
-
- eax = 0x80000001;
- ecx = 0;
- ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
- return edx & bit(X86_FEATURE_LM);
+ return ctxt->ops->guest_has_long_mode(ctxt);
#else
return false;
#endif
@@ -3618,18 +3613,11 @@ static int em_mov(struct x86_emulate_ctxt *ctxt)
return X86EMUL_CONTINUE;
}

-#define FFL(x) bit(X86_FEATURE_##x)
-
static int em_movbe(struct x86_emulate_ctxt *ctxt)
{
- u32 ebx, ecx, edx, eax = 1;
u16 tmp;

- /*
- * Check MOVBE is set in the guest-visible CPUID leaf.
- */
- ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
- if (!(ecx & FFL(MOVBE)))
+ if (!ctxt->ops->guest_has_movbe(ctxt))
return emulate_ud(ctxt);

switch (ctxt->op_bytes) {
@@ -4027,10 +4015,7 @@ static int em_movsxd(struct x86_emulate_ctxt *ctxt)

static int check_fxsr(struct x86_emulate_ctxt *ctxt)
{
- u32 eax = 1, ebx, ecx = 0, edx;
-
- ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
- if (!(edx & FFL(FXSR)))
+ if (!ctxt->ops->guest_has_fxsr(ctxt))
return emulate_ud(ctxt);

if (ctxt->ops->get_cr(ctxt, 0) & (X86_CR0_TS | X86_CR0_EM))
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8bb2fb1705ff..6bca14071d30 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6184,6 +6184,21 @@ static bool emulator_get_cpuid(struct x86_emulate_ctxt *ctxt,
return kvm_cpuid(emul_to_vcpu(ctxt), eax, ebx, ecx, edx, check_limit);
}

+static bool emulator_guest_has_long_mode(struct x86_emulate_ctxt *ctxt)
+{
+ return guest_cpuid_has(emul_to_vcpu(ctxt), X86_FEATURE_LM);
+}
+
+static bool emulator_guest_has_movbe(struct x86_emulate_ctxt *ctxt)
+{
+ return guest_cpuid_has(emul_to_vcpu(ctxt), X86_FEATURE_MOVBE);
+}
+
+static bool emulator_guest_has_fxsr(struct x86_emulate_ctxt *ctxt)
+{
+ return guest_cpuid_has(emul_to_vcpu(ctxt), X86_FEATURE_FXSR);
+}
+
static ulong emulator_read_gpr(struct x86_emulate_ctxt *ctxt, unsigned reg)
{
return kvm_register_read(emul_to_vcpu(ctxt), reg);
@@ -6261,6 +6276,9 @@ static const struct x86_emulate_ops emulate_ops = {
.fix_hypercall = emulator_fix_hypercall,
.intercept = emulator_intercept,
.get_cpuid = emulator_get_cpuid,
+ .guest_has_long_mode = emulator_guest_has_long_mode,
+ .guest_has_movbe = emulator_guest_has_movbe,
+ .guest_has_fxsr = emulator_guest_has_fxsr,
.set_nmi_mask = emulator_set_nmi_mask,
.get_hflags = emulator_get_hflags,
.set_hflags = emulator_set_hflags,
--
2.24.1
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