linux-kernel - Re: [PATCH] KVM: x86: User mutex guards to eliminate __kvm_x86_vendor

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Date:   Mon, 30 Oct 2023 18:17:16 +0200
From:   Nikolay Borisov <nik.borisov@...e.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     pbonzini@...hat.com, x86@...nel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: User mutex guards to eliminate
 __kvm_x86_vendor_init()



On 30.10.23 г. 18:07 ч., Sean Christopherson wrote:
> On Mon, Oct 30, 2023, Nikolay Borisov wrote:
>> Current separation between (__){0,1}kvm_x86_vendor_init() is superfluos as
> 
> superfluous
> 
> But this intro is actively misleading.  The double-underscore variant most definitely
> isn't superfluous, e.g. it eliminates the need for gotos reduces the probability
> of incorrect error codes, bugs in the error handling, etc.  It _becomes_ superflous
> after switching to guard(mutex).
> 
> IMO, this is one of the instances where the "problem, then solution" appoach is
> counter-productive.  If there are no objections, I'll massage the change log to
> the below when applying (for 6.8, in a few weeks).
> 
>    Use the recently introduced guard(mutex) infrastructure acquire and
>    automatically release vendor_module_lock when the guard goes out of scope.
>    Drop the inner __kvm_x86_vendor_init(), its sole purpose was to simplify
>    releasing vendor_module_lock in error paths.
> 
>    No functional change intended.

Thanks, I'm fine with this changelog.

> 
>> the the underscore version doesn't have any other callers.
>>
>> Instead, use the newly added cleanup infrastructure to ensure that
>> kvm_x86_vendor_init() holds the vendor_module_lock throughout its
>> exectuion and that in case of error in the middle it's released. No
>> functional changes.
>