[PATCH v3 1/5] KVM: x86: Add return value to kvm_cpuid().

Yu Zhang
2017-08-24T12:50:38Z

Return false in kvm_cpuid() when it fails to find the cpuid
entry. Also, this routine(and its caller) is optimized with
a new argument - check_limit, so that the check_cpuid_limit()
fall back can be avoided.

Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
---
arch/x86/include/asm/kvm_emulate.h | 4 ++--
arch/x86/kvm/cpuid.c | 17 +++++++++++++----
arch/x86/kvm/cpuid.h | 3 ++-
arch/x86/kvm/emulate.c | 12 ++++++------
arch/x86/kvm/svm.c | 2 +-
arch/x86/kvm/trace.h | 11 +++++++----
arch/x86/kvm/x86.c | 6 +++---
7 files changed, 34 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index fde36f1..fa2558e 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -219,8 +219,8 @@ struct x86_emulate_ops {
struct x86_instruction_info *info,
enum x86_intercept_stage stage);

- void (*get_cpuid)(struct x86_emulate_ctxt *ctxt,
- u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);
+ bool (*get_cpuid)(struct x86_emulate_ctxt *ctxt, u32 *eax, u32 *ebx,
+ u32 *ecx, u32 *edx, bool check_limit);
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/cpuid.c b/arch/x86/kvm/cpuid.c
index 59ca2ee..1450547 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -853,16 +853,24 @@ static struct kvm_cpuid_entry2* check_cpuid_limit(struct kvm_vcpu *vcpu,
return kvm_find_cpuid_entry(vcpu, maxlevel->eax, index);
}

-void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
+bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
+ u32 *ecx, u32 *edx, bool check_limit)
{
u32 function = *eax, index = *ecx;
struct kvm_cpuid_entry2 *best;
+ bool entry_found = true;

best = kvm_find_cpuid_entry(vcpu, function, index);

- if (!best)
+ if (!best) {
+ entry_found = false;
+ if (!check_limit)
+ goto out;
+
best = check_cpuid_limit(vcpu, function, index);
+ }

+out:
if (best) {
*eax = best->eax;
*ebx = best->ebx;
@@ -870,7 +878,8 @@ void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
*edx = best->edx;
} else
*eax = *ebx = *ecx = *edx = 0;
- trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx);
+ trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx, entry_found);
+ return entry_found;
}
EXPORT_SYMBOL_GPL(kvm_cpuid);

@@ -883,7 +892,7 @@ int kvm_emulate_cpuid(struct kvm_vcpu *vcpu)

eax = kvm_register_read(vcpu, VCPU_REGS_RAX);
ecx = kvm_register_read(vcpu, VCPU_REGS_RCX);
- kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx);
+ kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx, true);
kvm_register_write(vcpu, VCPU_REGS_RAX, eax);
kvm_register_write(vcpu, VCPU_REGS_RBX, ebx);
kvm_register_write(vcpu, VCPU_REGS_RCX, ecx);
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index ac15193..1ea3c0e 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -21,7 +21,8 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
struct kvm_cpuid2 *cpuid,
struct kvm_cpuid_entry2 __user *entries);
-void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);
+bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
+ u32 *ecx, u32 *edx, bool check_limit);

int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu);

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index fb00559..319d91f 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2333,7 +2333,7 @@ static int emulator_has_longmode(struct x86_emulate_ctxt *ctxt)

eax = 0x80000001;
ecx = 0;
- ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+ ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
return edx & bit(X86_FEATURE_LM);
}

@@ -2636,7 +2636,7 @@ static bool vendor_intel(struct x86_emulate_ctxt *ctxt)
u32 eax, ebx, ecx, edx;

eax = ecx = 0;
- ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+ ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
return ebx == X86EMUL_CPUID_VENDOR_GenuineIntel_ebx
&& ecx == X86EMUL_CPUID_VENDOR_GenuineIntel_ecx
&& edx == X86EMUL_CPUID_VENDOR_GenuineIntel_edx;
@@ -2656,7 +2656,7 @@ static bool em_syscall_is_enabled(struct x86_emulate_ctxt *ctxt)

eax = 0x00000000;
ecx = 0x00000000;
- ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+ ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
/*
* Intel ("GenuineIntel")
* remark: Intel CPUs only support "syscall" in 64bit
@@ -3551,7 +3551,7 @@ static int em_movbe(struct x86_emulate_ctxt *ctxt)
/*
* Check MOVBE is set in the guest-visible CPUID leaf.
*/
- ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+ ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
if (!(ecx & FFL(MOVBE)))
return emulate_ud(ctxt);

@@ -3865,7 +3865,7 @@ static int em_cpuid(struct x86_emulate_ctxt *ctxt)

eax = reg_read(ctxt, VCPU_REGS_RAX);
ecx = reg_read(ctxt, VCPU_REGS_RCX);
- ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+ ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, true);
*reg_write(ctxt, VCPU_REGS_RAX) = eax;
*reg_write(ctxt, VCPU_REGS_RBX) = ebx;
*reg_write(ctxt, VCPU_REGS_RCX) = ecx;
@@ -3924,7 +3924,7 @@ 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);
+ ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
if (!(edx & FFL(FXSR)))
return emulate_ud(ctxt);

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 3681287..be25072 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1561,7 +1561,7 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
}
init_vmcb(svm);

- kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy);
+ kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy, true);
kvm_register_write(vcpu, VCPU_REGS_RDX, eax);

if (kvm_vcpu_apicv_active(vcpu) && !init_event)
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 0a6cc67..8a202c4 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -151,8 +151,8 @@ TRACE_EVENT(kvm_fast_mmio,
*/
TRACE_EVENT(kvm_cpuid,
TP_PROTO(unsigned int function, unsigned long rax, unsigned long rbx,
- unsigned long rcx, unsigned long rdx),
- TP_ARGS(function, rax, rbx, rcx, rdx),
+ unsigned long rcx, unsigned long rdx, bool found),
+ TP_ARGS(function, rax, rbx, rcx, rdx, found),

TP_STRUCT__entry(
__field( unsigned int, function )
@@ -160,6 +160,7 @@ TRACE_EVENT(kvm_cpuid,
__field( unsigned long, rbx )
__field( unsigned long, rcx )
__field( unsigned long, rdx )
+ __field( bool, found )
),

TP_fast_assign(
@@ -168,11 +169,13 @@ TRACE_EVENT(kvm_cpuid,
__entry->rbx = rbx;
__entry->rcx = rcx;
__entry->rdx = rdx;
+ __entry->found = found;
),

- TP_printk("func %x rax %lx rbx %lx rcx %lx rdx %lx",
+ TP_printk("func %x rax %lx rbx %lx rcx %lx rdx %lx, cpuid entry %s",
__entry->function, __entry->rax,
- __entry->rbx, __entry->rcx, __entry->rdx)
+ __entry->rbx, __entry->rcx, __entry->rdx,
+ __entry->found ? "found" : "not found")
);

#define AREG(x) { APIC_##x, "APIC_" #x }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4e69923..cc2c7e4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5206,10 +5206,10 @@ static int emulator_intercept(struct x86_emulate_ctxt *ctxt,
return kvm_x86_ops->check_intercept(emul_to_vcpu(ctxt), info, stage);
}

-static void emulator_get_cpuid(struct x86_emulate_ctxt *ctxt,
- u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
+static bool emulator_get_cpuid(struct x86_emulate_ctxt *ctxt,
+ u32 *eax, u32 *ebx, u32 *ecx, u32 *edx, bool check_limit)
{
- kvm_cpuid(emul_to_vcpu(ctxt), eax, ebx, ecx, edx);
+ return kvm_cpuid(emul_to_vcpu(ctxt), eax, ebx, ecx, edx, check_limit);
}

static ulong emulator_read_gpr(struct x86_emulate_ctxt *ctxt, unsigned reg)
--
2.5.0