linux-kernel - Re: [PATCH 5/5] KVM: cpuid: remove has_leaf_count from struct kvm_cpuid

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Message-ID: <bb5e81f4-bb34-2841-0fa1-63876b97e54c@linux.intel.com>
Date:   Mon, 8 Jul 2019 15:09:01 +0800
From:   Jing Liu <jing2.liu@...ux.intel.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH 5/5] KVM: cpuid: remove has_leaf_count from struct
 kvm_cpuid_param

Hi Paolo,

On 7/4/2019 10:07 PM, Paolo Bonzini wrote:
> The has_leaf_count member was originally added for KVM's paravirtualization
> CPUID leaves.  However, since then the leaf count _has_ been added to those
> leaves as well, so we can drop that special case.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
[...]
> @@ -835,11 +834,10 @@ int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
>   	int limit, nent = 0, r = -E2BIG, i;
>   	u32 func;
>   	static const struct kvm_cpuid_param param[] = {
> -		{ .func = 0, .has_leaf_count = true },
> -		{ .func = 0x80000000, .has_leaf_count = true },
> -		{ .func = 0xC0000000, .qualifier = is_centaur_cpu, .has_leaf_count = true },
> +		{ .func = 0 },
> +		{ .func = 0x80000000 },
> +		{ .func = 0xC0000000, .qualifier = is_centaur_cpu },

>   		{ .func = KVM_CPUID_SIGNATURE },
> -		{ .func = KVM_CPUID_FEATURES },

It seems the two func are introduced by 2b5e97e, as paravirtual cpuid.
But when searching KVM_CPUID_SIGNATURE, there seems no caller requesting
this cpuid. Meanwhile, I felt curious if KVM_CPUID_FEATURES is still in 
use but it seems kvm_update_cpuid() uses that. Not sure which spec 
introduces the latest pv cpuid.

Thanks,
Jing

[...]