linux-kernel - Re: [PATCH 1/2] KVM: async_pf: Cleanup kvm_setup_async

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Message-ID: <42da32b0-6cb0-58e4-dbb0-484afbd48757@redhat.com>
Date:   Thu, 11 Jun 2020 02:07:03 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Vivek Goyal <vgoyal@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] KVM: async_pf: Cleanup kvm_setup_async_pf()

On 10/06/20 20:14, Sean Christopherson wrote:
>> -	/* setup delayed work */
>> +	/* Arch specific code should not do async PF in this case */
>> +	if (unlikely(kvm_is_error_hva(hva)))
> This feels like it should be changed to a WARN_ON_ONCE in a follow-up.
> With the WARN, the comment could probably be dropped.

I think a race is possible in principle where the memslots are changed
(for example) between s390's page fault handler and the gfn_to_hva call
in kvm_arch_setup_async_pf.

Queued both, thanks!

Paolo