linux-kernel - Re: [PATCH] KVM: Deal with nested sleeps in kvm_vcpu

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Message-ID: <8e8217f6-4eec-4793-637d-436a429c9aad@redhat.com>
Date:   Fri, 2 Dec 2022 19:26:59 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Space Meyer <spm@...gle.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        kpsingh@...nel.org
Subject: Re: [PATCH] KVM: Deal with nested sleeps in kvm_vcpu_block()

On 12/2/22 16:52, Space Meyer wrote:
> The bug doesn't seem to be easily reproducible, but looking at the
> code this should also be applicable for the upstream 6.0, 5.15, 5.10,
> 5.4, 4.19 and 4.14 branches, which have not received a backport of
> 26844fe.
> 
> Do you think this is all we should do? My conclusion from the LWN
> article was, that we should avoid the set_current_state ->
> conditional -> schedule pattern when possible as well.

Yes, the bug is there but unfortunately the backport is not easy.  I 
don't really feel confident backporting the fix to older kernels; even 
if it is apparently just a couple lines of code, event handling is very 
delicate and has had a lot of changes recently.

Paolo