linux-kernel - Re: [PATCH 0/2] KVM: x86: cleanup and fix userspace interrupt window

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Message-ID: <1eaaefbaf996f5e75d072863666aa3111d7b42f3.camel@infradead.org>
Date:   Fri, 27 Nov 2020 12:49:33 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     seanjc@...gle.com, Filippo Sironi <sironi@...zon.de>
Subject: Re: [PATCH 0/2] KVM: x86: cleanup and fix userspace interrupt window

On Fri, 2020-11-27 at 06:21 -0500, Paolo Bonzini wrote:
> This is my take on the split irqchip bug that David reported.  It's a
> much more complicated patch, but I think it really gets to the bottom
> of the issue and the code is clearer.

Looks good to me; thanks. With the exception of the stray apostrophe
already noted, both:

Reviewed-by: David Woodhouse <dwmw@...zon.co.uk>
Tested-by: David Woodhouse <dwmw@...zon.co.uk>

There is a slight caveat that I think we're accepting ExtINT from
userspace PIC sooner than we should, and queuing it up for delivery in
the kernel.

Whereas real hardware might not issue the INTA cycle to ask the PIC
what vector it wants until later. By which time the PIC might give a
different answer. But I don't think anyone cares, even if it can make
an observable difference in practice. And I'm not sure that it's new
with your patches either.

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