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

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Message-ID: <5621f716-1ab5-486f-ac8f-670cc68ee410@arm.com>
Date: Wed, 16 Oct 2024 15:41:31 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: 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>,
 Paolo Bonzini <pbonzini@...hat.com>
Cc: 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

+ Paolo Bonzini

This was a rather tricky series to get the recipients correct for and my script
did not realize that "supporter" was a pseudonym for "maintainer" so you were
missed off the original post. Appologies!

More context in cover letter:
https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/


On 14/10/2024 11:58, 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/
> 
>  virt/kvm/kvm_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index cb2b78e92910f..6c862bc41a672 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4244,7 +4244,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, unsigned long id)
>  		goto vcpu_decrement;
>  	}
>  
> -	BUILD_BUG_ON(sizeof(struct kvm_run) > PAGE_SIZE);
> +	BUILD_BUG_ON(sizeof(struct kvm_run) > PAGE_SIZE_MIN);
>  	page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
>  	if (!page) {
>  		r = -ENOMEM;