linux-kernel - Re: [RFC PATCH v1 17/57] kvm: Remove PAGE_SIZE compile-time constant assumption

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Message-ID: <ba0ddcf0-c251-46a0-8354-587e49c81399@arm.com>
Date: Tue, 15 Oct 2024 11:57:21 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Anshuman Khandual <anshuman.khandual@....com>,
 Ard Biesheuvel <ardb@...nel.org>, Catalin Marinas <catalin.marinas@....com>,
 David Hildenbrand <david@...hat.com>, Greg Marsden
 <greg.marsden@...cle.com>, Ivan Ivanov <ivan.ivanov@...e.com>,
 Kalesh Singh <kaleshsingh@...gle.com>, Marc Zyngier <maz@...nel.org>,
 Mark Rutland <mark.rutland@....com>, Matthias Brugger <mbrugger@...e.com>,
 Miroslav Benes <mbenes@...e.cz>, Will Deacon <will@...nel.org>,
 kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH v1 17/57] kvm: Remove PAGE_SIZE compile-time constant
 assumption

On 14/10/2024 22:37, Sean Christopherson wrote:
> Nit, "KVM:" for the scope.

Thanks, will fix.

> 
> On Mon, Oct 14, 2024, Ryan Roberts wrote:
>> To prepare for supporting boot-time page size selection, refactor code
>> to remove assumptions about PAGE_SIZE being compile-time constant. Code
>> intended to be equivalent when compile-time page size is active.
>>
>> Modify BUILD_BUG_ON() to compare with page size limit.
>>
>> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
>> ---
>>
>> ***NOTE***
>> Any confused maintainers may want to read the cover note here for context:
>> https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/
> 
> The patch should still stand on its own.  Most people can probably suss out what
> PAGE_SIZE_MIN is, but at the same time, it's quite easy to provide a more verbose
> changelog that's tailored to the actual patch.  E.g.
> 
>   To prepare for supporting boot-time page size selection, refactor KVM's
>   check on the size of the kvm_run structure to assert that the size is less
>   than the smallest possible page size, i.e. that kvm_run won't overflow its
>   page regardless of what page size is chosen at boot time.
> 
> With something like the above,
> 
> Reviewed-by: Sean Christopherson <seanjc@...gle.com>

Thanks! I'll update this for the next version.