From: Andrew Morton <akpm@linux-foundation.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Rob Landley <rob@landley.net>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, Arnd Bergmann <arnd@arndb.de>,
David Howells <dhowells@redhat.com>,
Akinobu Mita <akinobu.mita@gmail.com>,
Alexey Dobriyan <adobriyan@gmail.com>,
Herbert Xu <herbert@gondor.hengli.com.au>,
Stephen Rothwell <sfr@canb.auug.org.au>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org, Gleb Natapov <gleb@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, Avi Kivity <avi@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] bitops: add _local bitops
Date: Wed, 9 May 2012 12:19:40 -0700 [thread overview]
Message-ID: <20120509121940.459e93ba.akpm@linux-foundation.org> (raw)
In-Reply-To: <20120509134528.GA18044@redhat.com>
On Wed, 9 May 2012 16:45:29 +0300
"Michael S. Tsirkin" <mst@redhat.com> wrote:
> kvm needs to update some hypervisor variables atomically
> in a sense that the operation can't be interrupted
> in the middle. However the hypervisor always runs
> on the same CPU so it does not need any memory
> barrier or lock prefix.
Well. It adds more complexity, makes the kernel harder to understand
and maintain and introduces more opportunities for developers to add
bugs. So from that point of view, the best way of handling this patch
is to delete it.
Presumably the patch offers some benefit to offest all those costs.
But you didn't tell us what that benefit is, so we cannot make
a decision.
IOW: numbers, please. Convincing ones, for realistic test cases.
Secondly: can KVM just use __set_bit() and friends? I suspect those
interfaces happen to meet your requirements. At least on architectures
you care about.
next prev parent reply other threads:[~2012-05-09 19:19 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-09 13:45 [PATCH] bitops: add _local bitops Michael S. Tsirkin
2012-05-09 13:45 ` Michael S. Tsirkin
2012-05-09 14:03 ` H. Peter Anvin
2012-05-09 14:03 ` H. Peter Anvin
2012-05-09 15:06 ` Michael S. Tsirkin
2012-05-09 15:06 ` Michael S. Tsirkin
2012-05-09 15:43 ` Michael S. Tsirkin
2012-05-09 15:43 ` Michael S. Tsirkin
2012-05-09 15:44 ` H. Peter Anvin
2012-05-09 15:44 ` H. Peter Anvin
2012-05-09 15:47 ` Michael S. Tsirkin
2012-05-09 15:47 ` Michael S. Tsirkin
2012-05-09 16:24 ` H. Peter Anvin
2012-05-09 16:24 ` H. Peter Anvin
2012-05-09 16:36 ` Michael S. Tsirkin
2012-05-09 16:45 ` H. Peter Anvin
2012-05-09 16:45 ` H. Peter Anvin
2012-05-09 16:55 ` Michael S. Tsirkin
2012-05-09 16:55 ` Michael S. Tsirkin
2012-05-09 14:06 ` Arnd Bergmann
2012-05-09 14:06 ` Arnd Bergmann
2012-05-09 14:17 ` Avi Kivity
2012-05-09 19:19 ` Andrew Morton [this message]
2012-05-09 19:23 ` H. Peter Anvin
2012-05-09 19:23 ` H. Peter Anvin
2012-05-09 20:07 ` Michael S. Tsirkin
2012-05-09 20:10 ` H. Peter Anvin
2012-05-09 20:10 ` H. Peter Anvin
2012-05-09 20:12 ` Michael S. Tsirkin
2012-05-09 20:12 ` Michael S. Tsirkin
2012-05-10 9:26 ` Avi Kivity
2012-05-10 23:02 ` Benjamin Herrenschmidt
2012-05-10 17:38 ` Rob Landley
2012-05-10 17:38 ` Rob Landley
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120509121940.459e93ba.akpm@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=adobriyan@gmail.com \
--cc=akinobu.mita@gmail.com \
--cc=arnd@arndb.de \
--cc=avi@redhat.com \
--cc=dhowells@redhat.com \
--cc=gleb@redhat.com \
--cc=herbert@gondor.hengli.com.au \
--cc=hpa@zytor.com \
--cc=kvm@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=mst@redhat.com \
--cc=mtosatti@redhat.com \
--cc=pbonzini@redhat.com \
--cc=rob@landley.net \
--cc=sfr@canb.auug.org.au \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox