KVM Archive on lore.kernel.org
 help / color / Atom feed
From: Glauber Costa <glommer@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: mtosatti@redhat.com, avi@redhat.com, kvm@vger.kernel.org
Subject: Re: [PATCH kvm-unit-test 2/6] Introduce atomic operations
Date: Fri, 27 Aug 2010 08:39:30 -0300
Message-ID: <20100827113930.GN2985@mothafucka.localdomain> (raw)
In-Reply-To: <20100827054920.7409.41514.stgit@FreeLancer>

On Fri, Aug 27, 2010 at 01:49:20PM +0800, Jason Wang wrote:
> +u64 atomic64_cmpxchg(atomic64_t *v, u64 old, u64 new)
> +{
> +        u64 ret;
> +        u64 _old = old;
> +        u64 _new = new;
> +
> +        asm volatile("lock cmpxchgq %1,%2"
> +                     : "=a" (ret)
> +                     : "r" (_new),
> +                       "m" (*(volatile long *)&v->counter), "0"(_old)
> +                     : "memory"
> +                     );
> +        return ret;
> +}
> +
This is wrong.
See http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-tip.git;a=commitdiff;h=113fc5a6e8c2288619ff7e8187a6f556b7e0d372

you need to explicitly mark you are changing the memory, here.

Btw, this is mostly header copying, and can miss bug fixes like the one above. Isn't there
a way to just specify in the test they are needed, and then grab them from linux automatically?



  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-08-27  5:49 [PATCH kvm-unit-test 0/6] Kvmclock test Jason Wang
2010-08-27  5:49 ` [PATCH kvm-unit-test 1/6] Introduce memory barriers Jason Wang
2010-08-27  5:49 ` [PATCH kvm-unit-test 2/6] Introduce atomic operations Jason Wang
2010-08-27 11:39   ` Glauber Costa [this message]
2010-08-29  9:39     ` Avi Kivity
2010-08-27  5:49 ` [PATCH kvm-unit-test 3/6] Export tsc related helpers Jason Wang
2010-08-27  5:49 ` [PATCH kvm-unit-test 4/6] Introduce atol() Jason Wang
2010-08-27  5:49 ` [PATCH kvm-unit-test 5/6] Add a simple kvmclock driver Jason Wang
2010-08-27 11:31   ` Glauber Costa
2010-08-27  5:49 ` [PATCH kvm-unit-test 6/6] Add a test for kvm-clock Jason Wang
2010-08-27 11:27   ` Glauber Costa
2010-08-30  3:07     ` Jason Wang
2010-08-27 11:34   ` Glauber Costa
2010-08-30  3:27     ` Jason Wang
2010-08-28  1:58   ` Zachary Amsden

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=20100827113930.GN2985@mothafucka.localdomain \
    --to=glommer@redhat.com \
    --cc=avi@redhat.com \
    --cc=jasowang@redhat.com \
    --cc=kvm@vger.kernel.org \
    --cc=mtosatti@redhat.com \
    /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

KVM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvm/0 kvm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvm kvm/ https://lore.kernel.org/kvm \
		kvm@vger.kernel.org
	public-inbox-index kvm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.kvm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git