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SubjectRe: [PATCH 03/61] KVM: x86: Simplify handling of Centaur CPUID leafs
Date
Sean Christopherson <sean.j.christopherson@intel.com> writes:

> Refactor the handling of the Centaur-only CPUID leaf to detect the leaf
> via a runtime query instead of adding a one-off callback in the static
> array. When the callback was introduced, there were additional fields
> in the array's structs, and more importantly, retpoline wasn't a thing.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/kvm/cpuid.c | 32 ++++++++++----------------------
> 1 file changed, 10 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index f49fdd06f511..de52cbb46171 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -829,15 +829,7 @@ static int do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 func,
> return __do_cpuid_func(entry, func, nent, maxnent);
> }
>
> -struct kvm_cpuid_param {
> - u32 func;
> - bool (*qualifier)(const struct kvm_cpuid_param *param);
> -};
> -
> -static bool is_centaur_cpu(const struct kvm_cpuid_param *param)
> -{
> - return boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR;
> -}
> +#define CENTAUR_CPUID_SIGNATURE 0xC0000000

arch/x86/kernel/cpu/centaur.c also hardcodes the value, would make sense
to put it to some x86 header instead.

>
> static int get_cpuid_func(struct kvm_cpuid_entry2 *entries, u32 func,
> int *nent, int maxnent, unsigned int type)
> @@ -845,6 +837,10 @@ static int get_cpuid_func(struct kvm_cpuid_entry2 *entries, u32 func,
> u32 limit;
> int r;
>
> + if (func == CENTAUR_CPUID_SIGNATURE &&
> + boot_cpu_data.x86_vendor != X86_VENDOR_CENTAUR)
> + return 0;
> +
> r = do_cpuid_func(&entries[*nent], func, nent, maxnent, type);
> if (r)
> return r;
> @@ -896,11 +892,8 @@ int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
> struct kvm_cpuid_entry2 *cpuid_entries;
> int nent = 0, r = -E2BIG, i;
>
> - static const struct kvm_cpuid_param param[] = {
> - { .func = 0 },
> - { .func = 0x80000000 },
> - { .func = 0xC0000000, .qualifier = is_centaur_cpu },
> - { .func = KVM_CPUID_SIGNATURE },
> + static const u32 funcs[] = {
> + 0, 0x80000000, CENTAUR_CPUID_SIGNATURE, KVM_CPUID_SIGNATURE,
> };
>
> if (cpuid->nent < 1)
> @@ -918,14 +911,9 @@ int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
> goto out;
>
> r = 0;
> - for (i = 0; i < ARRAY_SIZE(param); i++) {
> - const struct kvm_cpuid_param *ent = &param[i];
> -
> - if (ent->qualifier && !ent->qualifier(ent))
> - continue;
> -
> - r = get_cpuid_func(cpuid_entries, ent->func, &nent,
> - cpuid->nent, type);
> + for (i = 0; i < ARRAY_SIZE(funcs); i++) {
> + r = get_cpuid_func(cpuid_entries, funcs[i], &nent, cpuid->nent,
> + type);
> if (r)
> goto out_free;
> }

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

--
Vitaly

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