linux-kernel - Re: [PATCH 09/61] KVM: x86: Refactor CPUID 0xD.N sub-leaf entry creation

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Date:   Fri, 07 Feb 2020 16:56:30 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH 09/61] KVM: x86: Refactor CPUID 0xD.N sub-leaf entry creation

Sean Christopherson <sean.j.christopherson@...el.com> writes:

> Increment the number of CPUID entries immediately after do_host_cpuid()
> in preparation for moving the logic into do_host_cpuid().  Handle the
> rare/impossible case of encountering a bogus sub-leaf by decrementing
> the number entries on failure.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/kvm/cpuid.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 424dde41cb5d..6e1685a16cca 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -677,6 +677,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
>  				goto out;
>  
>  			do_host_cpuid(&entry[i], function, idx);
> +			++*nent;
>  
>  			/*
>  			 * The @supported check above should have filtered out
> @@ -685,12 +686,13 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
>  			 * reach this point, and they should have a non-zero
>  			 * save state size.
>  			 */
> -			if (WARN_ON_ONCE(!entry[i].eax || (entry[i].ecx & 1)))
> +			if (WARN_ON_ONCE(!entry[i].eax || (entry[i].ecx & 1))) {
> +				--*nent;
>  				continue;
> +			}
>  
>  			entry[i].ecx = 0;
>  			entry[i].edx = 0;
> -			++*nent;
>  			++i;
>  		}
>  		break;

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

-- 
Vitaly