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    SubjectRe: [PATCH 03/61] KVM: x86: Simplify handling of Centaur CPUID leafs
    On Thu, Feb 06, 2020 at 04:05:54PM +0100, Vitaly Kuznetsov wrote:
    > 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.

    Ya, I just didn't want to touch non-KVM code in a 60+ patch series.

    > > 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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