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Date: Mon, 24 Feb 2020 23:25:24 +0100 From: Vitaly Kuznetsov <vkuznets@...hat.com> To: Sean Christopherson <sean.j.christopherson@...el.com> Cc: Paolo Bonzini <pbonzini@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 46/61] KVM: x86: Remove the unnecessary loop on CPUID 0x7 sub-leafs Sean Christopherson <sean.j.christopherson@...el.com> writes: > Explicitly handle CPUID 0x7 sub-leaf 1. The kernel is currently aware > of exactly one feature in CPUID 0x7.1, which means there is room for > another 127 features before CPUID 0x7.2 will see the light of day, i.e. > the looping is likely to be dead code for years to come. > > Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com> > --- > arch/x86/kvm/cpuid.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 7362e5238799..47f61f4497fb 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -533,11 +533,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) > if (boot_cpu_has(X86_FEATURE_AMD_SSBD)) > cpuid_entry_set(entry, X86_FEATURE_SPEC_CTRL_SSBD); > > - for (i = 1, max_idx = entry->eax; i <= max_idx; i++) { > - if (WARN_ON_ONCE(i > 1)) > - break; > - > - entry = do_host_cpuid(array, function, i); > + /* KVM only supports 0x7.0 and 0x7.1, capped above via min(). */ > + if (entry->eax == 1) { > + entry = do_host_cpuid(array, function, 1); > if (!entry) > goto out; Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com> -- Vitaly
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