linux-kernel - Re: [PATCH v3 02/15] KVM: arm64: Add "struct kvm_page

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Message-ID: <aFMS4O2TkWN8nexY@linux.dev>
Date: Wed, 18 Jun 2025 12:26:24 -0700
From: Oliver Upton <oliver.upton@...ux.dev>
To: James Houghton <jthoughton@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Jonathan Corbet <corbet@....net>, Marc Zyngier <maz@...nel.org>,
	Yan Zhao <yan.y.zhao@...el.com>,
	Nikita Kalyazin <kalyazin@...zon.com>,
	Anish Moorthy <amoorthy@...gle.com>,
	Peter Gonda <pgonda@...gle.com>, Peter Xu <peterx@...hat.com>,
	David Matlack <dmatlack@...gle.com>, wei.w.wang@...el.com,
	kvm@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev
Subject: Re: [PATCH v3 02/15] KVM: arm64: Add "struct kvm_page_fault" to
 gather common fault variables

On Wed, Jun 18, 2025 at 04:24:11AM +0000, James Houghton wrote:
> From: Sean Christopherson <seanjc@...gle.com>
> 
> Introduce "struct kvm_page_fault" and use it in user_mem_abort() in lieu
> of a collection of local variables.  Providing "struct kvm_page_fault"
> will allow common KVM to provide APIs to take in said structure, e.g. when
> preparing memory fault exits.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: James Houghton <jthoughton@...gle.com>
> ---
>  arch/arm64/include/asm/kvm_host.h |  9 +++++++++
>  arch/arm64/kvm/mmu.c              | 32 +++++++++++++++++--------------
>  2 files changed, 27 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 6ce2c51734820..ae83d95d11b74 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -413,6 +413,15 @@ struct kvm_vcpu_fault_info {
>  	u64 disr_el1;		/* Deferred [SError] Status Register */
>  };
>  
> +struct kvm_page_fault {
> +	const bool exec;
> +	const bool write;
> +	const bool is_private;
> +
> +	gfn_t gfn;
> +	struct kvm_memory_slot *slot;
> +};
> +

So this seems to cherry-pick "interesting" values into the structure but
leaves the rest of the abort context scattered about in locals. If we're
going to do something like this I'd rather have a wholesale refactoring
than just the bits to intersect with x86 (more on that later...)

Thanks,
Oliver