linux-kernel - Re: [GIT PULL] KVM updates for the 2.6.38 merge window

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Message-ID: <AANLkTimLJnV9oJwnaN+jdvNus4cxuqvgUqHUwi7vpqBe@mail.gmail.com>
Date:	Wed, 12 Jan 2011 12:53:14 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Rik van Riel <riel@...hat.com>
Cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>
Subject: Re: [GIT PULL] KVM updates for the 2.6.38 merge window

On Wed, Jan 12, 2011 at 12:33 PM, Rik van Riel <riel@...hat.com> wrote:
>
> Now that we have FAULT_FLAG_ALLOW_RETRY, the async
> pagefault patches can be a little smaller.

I suspect you do still want a new page flag, to say that
FAULT_FLAG_ALLOW_RETRY shouldn't actually wait for the page that it
allows retry for.

But even then, that flag should not be named "MINOR", it should be
about what the behaviour is actually all about ("NOWAIT_RETRY" or
whatever - it presumably would also cause us to not drop the
mmap_sem).

IOW, these days I suspect the patch _should_ look something like the attached.

Anyway, with this, you should be able to use

  FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT

to basically get a non-waiting page fault (and it will return the
VM_FAULT_RETRY error code if it failed).

NOTE! TOTALLY UNTESTED!

                       Linus

View attachment "patch.diff" of type "text/x-patch" (1116 bytes)