linux-kernel - Re: [PATCH v8 1/5] mm: introduce a common interface for balloon pages mobility

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20120823172844.GC10777@t510.redhat.com>
Date:	Thu, 23 Aug 2012 14:28:45 -0300
From:	Rafael Aquini <aquini@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Minchan Kim <minchan@...nel.org>
Subject: Re: [PATCH v8 1/5] mm: introduce a common interface for balloon
 pages mobility

On Thu, Aug 23, 2012 at 07:25:05PM +0300, Michael S. Tsirkin wrote:
> On Thu, Aug 23, 2012 at 04:53:28PM +0300, Michael S. Tsirkin wrote:
> > Basically it was very simple: we assumed page->lru was never
> > touched for an allocated page, so it's safe to use it for
> > internal book-keeping by the driver.
> > 
> > Now, this is not the case anymore, you add some logic in mm/ that might
> > or might not touch page->lru depending on things like reference count.
> 
> Another thought: would the issue go away if balloon used
> page->private to link pages instead of LRU?
> mm core could keep a reference on page to avoid it
> being used while mm handles it (maybe it does already?).
>
I don't think so. That would be a lot more trikier and complex, IMHO.
 
> If we do this, will not the only change to balloon be to tell mm that it
> can use compaction for these pages when it allocates the page: using
> some GPF flag or a new API?
> 

What about keep a conter at virtio_balloon structure on how much pages are
isolated from balloon's list and check it at leak time?
if the counter gets > 0 than we can safely put leak_balloon() to wait until
balloon page list gets completely refilled. I guess that is simple to get
accomplished and potentially addresses all your concerns on this issue.

Cheers!

--
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/