linux-kernel - Re: [RFC][PATCH] virtio balloon: kill tell-host-first logic

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87ei5bdosp.fsf@rustcorp.com.au>
Date:	Sun, 10 Apr 2011 08:18:22 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, Dave Hansen <dave@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH] virtio balloon: kill tell-host-first logic

On Thu, 07 Apr 2011 10:43:25 -0700, Dave Hansen <dave@...ux.vnet.ibm.com> wrote:
> 
> The virtio balloon driver has a VIRTIO_BALLOON_F_MUST_TELL_HOST
> feature bit.  Whenever the bit is set, we must always tell the
> host before we free pages back to the allocator.  Without this
> we might free a page (and have another user touch it) while the
> hypervisor is unprepared for it.
> 
> But, if the bit is _not_ set, we are under no obligation to
> reverse the order.  Furthermore, all modern qemus set this bit.
> So, the "tell second" code is completely unused and untestable.
> Quoting Anthony: "untested code is broken code".
> 
> This _also_ means that we don't have to preserve a pfn list
> after the pages are freed, which should let us get rid of some
> temporary storage (vb->pfns) eventually.
> 
> Signed-off-by: Dave Hansen <dave@...ux.vnet.ibm.com>

Thanks, applied!

Rusty.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/