linux-kernel - Re: [PATCH RFCv2 9/9] arm64: Support async page fault

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Message-ID: <8ab64c6a-582b-691d-79ab-21cdc0455cd3@redhat.com>
Date:   Thu, 28 May 2020 12:48:52 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Gavin Shan <gshan@...hat.com>, kvmarm@...ts.cs.columbia.edu
Cc:     maz@...nel.org, linux-kernel@...r.kernel.org, shan.gavin@...il.com,
        catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH RFCv2 9/9] arm64: Support async page fault

On 28/05/20 08:14, Gavin Shan wrote:
>> - for x86 we're also thinking of initiating the page fault from the
>> exception handler, rather than doing so from the hypervisor before
>> injecting the exception.  If ARM leads the way here, we would do our
>> best to share code when x86 does the same.
> 
> Sorry, Paolo, I don't follow your idea here. Could you please provide
> more details?

The idea is to inject stage2 page faults into the guest even before the
host starts populates the page.  The guest then invokes a hypercall,
telling the host to populate the page table and inject the 'page ready'
event (interrupt) when it's done.

For x86 the advantage is that the processor can take care of raising the
stage2 page fault in the guest, so it's faster.

Paolo