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SubjectRe: [PATCH 26/61] KVM: x86: Introduce cpuid_entry_{get,has}() accessors
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On 2/2/2020 2:51 AM, Sean Christopherson wrote:
> Introduce accessors to retrieve feature bits from CPUID entries and use
> the new accessors where applicable. Using the accessors eliminates the
> need to manually specify the register to be queried at no extra cost
> (binary output is identical) and will allow adding runtime consistency
> checks on the function and index in a future patch.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/kvm/cpuid.c | 9 +++++----
> arch/x86/kvm/cpuid.h | 46 +++++++++++++++++++++++++++++++++++---------
> 2 files changed, 42 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index e3026fe638aa..3316963dad3d 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -68,7 +68,7 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
> best->edx |= F(APIC);
>
> if (apic) {
> - if (best->ecx & F(TSC_DEADLINE_TIMER))
> + if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
> apic->lapic_timer.timer_mode_mask = 3 << 17;
> else
> apic->lapic_timer.timer_mode_mask = 1 << 17;
> @@ -96,7 +96,8 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
> }
>
> best = kvm_find_cpuid_entry(vcpu, 0xD, 1);
> - if (best && (best->eax & (F(XSAVES) | F(XSAVEC))))
> + if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
> + cpuid_entry_has(best, X86_FEATURE_XSAVEC)))
> best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
>
> /*
> @@ -155,7 +156,7 @@ static void cpuid_fix_nx_cap(struct kvm_vcpu *vcpu)
> break;
> }
> }
> - if (entry && (entry->edx & F(NX)) && !is_efer_nx()) {
> + if (entry && cpuid_entry_has(entry, X86_FEATURE_NX) && !is_efer_nx()) {
> entry->edx &= ~F(NX);
> printk(KERN_INFO "kvm: guest NX capability removed\n");
> }
> @@ -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);
> 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 I cannot image other possible use case of it.

> +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. :)

> +{
> + 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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