linux-kernel - Re: [patch 14/31] x86/fpu: Replace KVMs homebrewn FPU copy from user

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Message-ID: <9adb43fb-182f-dffb-1fde-ae7e9610a344@redhat.com>
Date:   Wed, 13 Oct 2021 17:12:21 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        "Chang S. Bae" <chang.seok.bae@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        kvm@...r.kernel.org
Subject: Re: [patch 14/31] x86/fpu: Replace KVMs homebrewn FPU copy from user

On 13/10/21 16:57, Sean Christopherson wrote:
>>> +int fpu_copy_kvm_uabi_to_vcpu(struct fpu *fpu, const void *buf, u64 xcr0,
>>> +			      u32 *vpkru)
>> Right, except that there's no @vcpu in the args of that function. I
>> guess you could call it
>>
>> fpu_copy_kvm_uabi_to_buf()
>>
>> and that @buf can be
>>
>> vcpu->arch.guest_fpu
> But the existing @buf is the userspace pointer, which semantically makes sense
> because the userspace pointer is the "buffer" and the destination @fpu (and @prku)
> is vCPU state, not a buffer.
> 
> That said, I also struggled with the lack of @vcpu.  What about prepending vcpu_
> to fpu and to pkru?  E.g.
> 
>    int fpu_copy_kvm_uabi_to_vcpu(struct fpu *vcpu_fpu, const void *buf, u64 xcr0,
>    				u32 *vcpu_pkru)
> 

It doesn't matter much that the source is somehow related to a vCPU, as 
long as the FPU is concerned.  If anything I would even drop the "v" 
from vpkru, but that's really nitpicking.

Paolo