linux-kernel - Re: [RESENDx2] [PULL] virtio: fix barriers for virtio-mmio

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Message-ID: <CA+55aFyvMkAtXPRxiFR+UpZKGHMhp8Vd9aYg1dkaoKMwD5MLcw@mail.gmail.com>
Date:	Fri, 23 Dec 2011 01:31:12 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	linux-kernel@...r.kernel.org,
	virtualization <virtualization@...ts.linux-foundation.org>
Subject: Re: [RESENDx2] [PULL] virtio: fix barriers for virtio-mmio

On Thu, Dec 22, 2011 at 9:16 PM, Rusty Russell <rusty@...tcorp.com.au> wrote:
> This one as a signed tag on github, in case the inline patch was
> the reason you dropped this.

No, and please why do you make your tag-names be your email address?
That's just odd. It seems to be related to some broken SCM system that
thinks that tag-names are global and somehow different from
branch-names.

No, the reason I didn't pull was that the games with the barriers just
threw me off. They seem hacky and disgusting beyond words. And afaik
there are no actual *devices* that implement virtio-mmu, and the
commit that adds the mmu thing talks about qemu interfaces to. So it's
still just virtual, which makes the whole thing just masturbatory,
afaik. There's nothing out-of-order in virtual mmio.

So the whole thing looks confused. There's never any reason to
actually use the expensive sfence/rfences at all. Afaik you still just
want smp_*mb() for all cases.

                  Linus
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