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SubjectRe: [PATCH 26/61] KVM: x86: Introduce cpuid_entry_{get,has}() accessors
On Fri, Feb 14, 2020 at 05:44:41PM +0800, Xiaoyao Li wrote:
> On 2/2/2020 2:51 AM, Sean Christopherson wrote:
> >@@ -387,7 +388,7 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry)
> > entry->ebx |= F(TSC_ADJUST);
> > entry->ecx &= kvm_cpuid_7_0_ecx_x86_features;
> >- f_la57 = entry->ecx & F(LA57);
> >+ f_la57 = cpuid_entry_get(entry, X86_FEATURE_LA57);

Note, cpuid_entry_get() is used here.

> > cpuid_mask(&entry->ecx, CPUID_7_ECX);
> > /* Set LA57 based on hardware capability. */
> > entry->ecx |= f_la57;
> >diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
> >index 72a79bdfed6b..64e96e4086e2 100644
> >--- a/arch/x86/kvm/cpuid.h
> >+++ b/arch/x86/kvm/cpuid.h
> >@@ -95,16 +95,10 @@ static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned x86_feature)
> > return reverse_cpuid[x86_leaf];
> > }
> >-static __always_inline u32 *guest_cpuid_get_register(struct kvm_vcpu *vcpu, unsigned x86_feature)
> >+static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
> >+ const struct cpuid_reg *cpuid)
> > {
> >- struct kvm_cpuid_entry2 *entry;
> >- const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
> >-
> >- entry = kvm_find_cpuid_entry(vcpu, cpuid.function, cpuid.index);
> >- if (!entry)
> >- return NULL;
> >-
> >- switch (cpuid.reg) {
> >+ switch (cpuid->reg) {
> > case CPUID_EAX:
> > return &entry->eax;
> > case CPUID_EBX:
> >@@ -119,6 +113,40 @@ static __always_inline u32 *guest_cpuid_get_register(struct kvm_vcpu *vcpu, unsi
> > }
> > }
> >+static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
> >+ unsigned x86_feature)
> >+{
> >+ const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
> >+
> >+ return __cpuid_entry_get_reg(entry, &cpuid);
> >+}
> >+
> >+static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry,
> >+ unsigned x86_feature)
> >+{
> >+ u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
> >+
> >+ return *reg & __feature_bit(x86_feature);
> >+}
> >+
>
> This helper function is unnecessary. There is only one user throughout this
> series, i.e., cpuid_entry_has() below.

And the LA57 case above.

> And I cannot image other possible use case of it.

The LA57 case, which admittedly goes away soon, was subtle enough (OR in
the flag instead of querying yes/no) that I wanted keep the accessor around
in case a similar case popped up in the future.

> >+static __always_inline bool cpuid_entry_has(struct kvm_cpuid_entry2 *entry,
> >+ unsigned x86_feature)
> >+{
> >+ return cpuid_entry_get(entry, x86_feature);
> >+}
> >+
> >+static __always_inline int *guest_cpuid_get_register(struct kvm_vcpu *vcpu, unsigned x86_feature)
> ^
> Should be u32
> otherwise, previous patch will be unhappy. :)

Doh, thanks!

> >+{
> >+ struct kvm_cpuid_entry2 *entry;
> >+ const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
> >+
> >+ entry = kvm_find_cpuid_entry(vcpu, cpuid.function, cpuid.index);
> >+ if (!entry)
> >+ return NULL;
> >+
> >+ return __cpuid_entry_get_reg(entry, &cpuid);
> >+}
> >+
> > static __always_inline bool guest_cpuid_has(struct kvm_vcpu *vcpu, unsigned x86_feature)
> > {
> > u32 *reg;
> >
>

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