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KVM: x86: Add dedicated emulator helpers for querying CPUID features 

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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2019-12-17 13:32:38 -08:00 committed by Paolo Bonzini
parent 345599f9a2
commit 5ae78e95ed
3 changed files with 25 additions and 18 deletions
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4
arch/x86/include/asm/kvm_emulate.h
View File

@ -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);

21
arch/x86/kvm/emulate.c
View File

@ -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))

18
arch/x86/kvm/x86.c
View File

@ -6245,6 +6245,21 @@ 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);
@ -6322,6 +6337,9 @@ 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,