linux-kernel - Re: [PATCH 1/6] KVM: arm64: Add __gmem_abort and __user_mem

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Message-ID: <aMMUiyPLd1-_-V5p@linux.dev>
Date: Thu, 11 Sep 2025 11:27:23 -0700
From: Oliver Upton <oliver.upton@...ux.dev>
To: Jack Thomson <jackabt.amazon@...il.com>
Cc: maz@...nel.org, pbonzini@...hat.com, joey.gouly@....com,
	suzuki.poulose@....com, yuzenghui@...wei.com,
	catalin.marinas@....com, will@...nel.org, shuah@...nel.org,
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
	isaku.yamahata@...el.com, roypat@...zon.co.uk,
	kalyazin@...zon.co.uk, jackabt@...zon.com
Subject: Re: [PATCH 1/6] KVM: arm64: Add __gmem_abort and __user_mem_abort

Hi Jack,

On Thu, Sep 11, 2025 at 02:46:43PM +0100, Jack Thomson wrote:
> From: Jack Thomson <jackabt@...zon.com>
> 
> Adding __gmem_abort and __user_mem_abort that preserve -EAGAIN results.
> These will be used by the pre-fault implementation which needs to retry
> on -EAGAIN.

-EAGAIN is a pretty clear signal that another vCPU has faulted on this
memory and is in the middle of installing a mapping. Why bother with
retrying?

If we conceptually treat this thing as a synthetic stage-2 abort then it
should use the same EAGAIN handling as a literal stage-2 abort.

Thanks,
Oliver