linux-kernel - Re: [PATCH 1/1] KVM: x86/mmu: Fix TLB flush range when handling disconnected pt

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Date:   Tue, 16 Nov 2021 18:55:13 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Ben Gardon <bgardon@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Peter Xu <peterx@...hat.com>, Peter Shier <pshier@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Mingwei Zhang <mizhang@...gle.com>,
        Yulei Zhang <yulei.kernel@...il.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>,
        Kai Huang <kai.huang@...el.com>,
        Keqian Zhu <zhukeqian1@...wei.com>,
        David Hildenbrand <david@...hat.com>, stable@...r.kernel.org
Subject: Re: [PATCH 1/1] KVM: x86/mmu: Fix TLB flush range when handling
 disconnected pt

On 11/16/21 18:29, Ben Gardon wrote:
>> TL;DR: this type of optional refactoring doesn't belong in a patch Cc'd for stable,
>> and my personal preference is to always declare variables at function scope (it's
>> not a hard rule though, Paolo has overruled me at least once:-)  ).
>
> That makes sense. I don't have a preference either way. Paolo, if you
> want the version without the refactor, the version I sent in the RFC
> should be good. If the refactor is desired, I can separate it out into
> another patch and send a v2 of this patch as a mini series, tagging
> only the fix for stable.

It's really a damned-if-you-do/damned-if-you-don't situation.  And also 
keeping the patch as similar as possible in stable has the advantage 
that future backports have a slightly lower chance of breaking due to 
shadowed variables.

In the end I agree with both of you :) and in this case I tend to accept 
the patch as written.  So I queued it, though it probably will not be in 
the immediately next pull request.

My plan for the next couple days is to send a pull request and finally 
move the development tree to 5.16-rc1, so that I can push to kvm/next 
all the SVM, memslot and xarray stuff that's pending.  Then I'll go back 
to this one.

Paolo

> I've generally preferred declaring variables at function scope too
> since that seems like the overwhelming convention, but it's always
> struck me as a bit of a waste to not make use of scoping rules more.
> It does make it nice and clear how things should be laid out when
> debugging the kernel with GDB or something though.
> 
> In any case, please let me know how you'd like the changes organized
> and I can send up follow ups as needed, or we can just move forward
> with the RFC version.
>