linux-kernel - Re: [RFC PATCH v6 07/32] KVM: x86: apic_test

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Message-ID: <175b29fa-40b4-46c7-b33f-ad6ffe89a33c@amd.com>
Date: Tue, 10 Jun 2025 09:56:03 +0530
From: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org,
 tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
 Thomas.Lendacky@....com, nikunj@....com, Santosh.Shukla@....com,
 Vasant.Hegde@....com, Suravee.Suthikulpanit@....com, David.Kaplan@....com,
 x86@...nel.org, hpa@...or.com, peterz@...radead.org, pbonzini@...hat.com,
 kvm@...r.kernel.org, kirill.shutemov@...ux.intel.com, huibo.wang@....com,
 naveen.rao@....com, francescolavra.fl@...il.com, tiala@...rosoft.com
Subject: Re: [RFC PATCH v6 07/32] KVM: x86: apic_test_vector() to common code



On 6/7/2025 12:26 AM, Sean Christopherson wrote:
> On Fri, Jun 06, 2025, Sean Christopherson wrote:
>> Actually, looking at the end usage, just drop VEC_POS/REG_POS entirely.  IIRC, I
>> suggested keeping the shorthand versions for KVM, but I didn't realize there would
>> literally be two helpers left.  At that point, keeping VEC_POS and REG_POS is
>> pure stubborness :-)
>>
>>  1. Rename VEC_POS/REG_POS => APIC_VECTOR_TO_BIT_NUMBER/APIC_VECTOR_TO_REG_OFFSET
>>  2. Rename all of the KVM helpers you intend to move out of KVM.
> 
> Looking at the earlier patches again, I vote to add a 4th:
> 
>    2a. Replace all "char *" with "void *" in all affected helpers.
> 
> Pointer arithmetic for "void *" and "char *" operate identically, and AFAICT that's
> the only reason why e.g. __kvm_lapic_set_reg64() takes a "char *".  That way there
> is even less of a chance of doing the wrong thing, e.g. neglecting to cast and
> reading a byte instead of the desired size.
>

Sounds good. Will include this in the next version.


- Neeraj
 
>>  3. Move all of the helpers out of KVM.