linux-kernel - Re: [PATCH] Add a page cache-backed balloon device driver.

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: <CAK+C7kXSL=nqb1ZzY9MLB_02G_J-p3PCqaLf8CNJWcV8nsz=2w@mail.gmail.com>
Date:	Wed, 27 Jun 2012 09:08:37 -0700
From:	Frank Swiderski <fes@...gle.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>, riel@...hat.com,
	Andrea Arcangeli <aarcange@...hat.com>,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org, mikew@...gle.com
Subject: Re: [PATCH] Add a page cache-backed balloon device driver.

On Wed, Jun 27, 2012 at 9:06 AM, Michael S. Tsirkin <mst@...hat.com> wrote:
> On Wed, Jun 27, 2012 at 08:48:55AM -0700, Frank Swiderski wrote:
>> On Tue, Jun 26, 2012 at 7:56 PM, Rusty Russell <rusty@...tcorp.com.au> wrote:
>> > On Wed, 27 Jun 2012 00:41:06 +0300, "Michael S. Tsirkin" <mst@...hat.com> wrote:
>> >> On Tue, Jun 26, 2012 at 01:32:58PM -0700, Frank Swiderski wrote:
>> >> > This implementation of a virtio balloon driver uses the page cache to
>> >> > "store" pages that have been released to the host.  The communication
>> >> > (outside of target counts) is one way--the guest notifies the host when
>> >> > it adds a page to the page cache, allowing the host to madvise(2) with
>> >> > MADV_DONTNEED.  Reclaim in the guest is therefore automatic and implicit
>> >> > (via the regular page reclaim).  This means that inflating the balloon
>> >> > is similar to the existing balloon mechanism, but the deflate is
>> >> > different--it re-uses existing Linux kernel functionality to
>> >> > automatically reclaim.
>> >> >
>> >> > Signed-off-by: Frank Swiderski <fes@...gle.com>
>> >>
>> >> I'm pondering this:
>> >>
>> >> Should it really be a separate driver/device ID?
>> >> If it behaves the same from host POV, maybe it
>> >> should be up to the guest how to inflate/deflate
>> >> the balloon internally?
>> >
>> > Well, it shouldn't steal ID 10, either way :)  Either use a completely
>> > bogus number, or ask for an id.
>> >
>> > But AFAICT this should be a an alternate driver of for the same device:
>> > it's not really a separate device, is it?
>> >
>> > Cheers,
>> > Rusty.
>>
>> Apologies, Rusty.  Asking for an ID is in the virtio spec, and I
>> completely neglected that step.  Though as you and others have pointed
>> out, this probably fits better as a different driver for the same
>> device.  Since it changes whether or not the deflate operation is
>> necessary, it also seems that how this should look is different
>> behavior based on a feature bit in the device.
>>
>> If that sounds reasonable, then what I'll do with this patch is merge
>> it with the existing virtio balloon driver with a feature bit for
>> determining which behavior to use.
>>
>> I also think the idea of a generic balloon that the different balloon
>> drivers use for the inflate/deflate operations is interesting and
>> useful, though I think the suggestion of pending that until later is
>> correct.
>>
>> Sounds reasonable?
>>
>> Regards,
>> fes
>
> I think a spec patch would be a good spec at this point.
> You can get the spec from Rusty, or a mirror
> from my git:
>
> git://git.kernel.org/pub/scm/virt/kvm/mst/virtio-spec.git
>
>
>


Got it, thanks, will do.

Regards,
fes
--
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/