linux-kernel - Re: [PATCH 3/4] KVM: Switch to srcu-less get_dirty

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: <4F66FDB9.1000306@linux.vnet.ibm.com>
Date:	Mon, 19 Mar 2012 17:34:49 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
CC:	avi@...hat.com, mtosatti@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] KVM: Switch to srcu-less get_dirty_log()

On 03/16/2012 05:44 PM, Takuya Yoshikawa wrote:

> On Fri, 16 Mar 2012 16:28:56 +0800
> Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com> wrote:
> 
>> Thanks for your explanation, maybe you are right, i do not know migration
>> much.
>>
>> What i worried about is, you have changed the behaviour of GET_DIRTY_LOG,
>> in the current one, it can get all the dirty pages when it is called; after
>> your change, GET_DIRTY_LOG can get a empty dirty bitmap but dirty page exists.
> 
> The current code also see the same situation because nothing prevents the
> guest from writing to pages before GET_DIRTY_LOG returns and the userspace
> checks the bitmap.  Everything is running.
> 


The current code is under the protection of s-rcu:
IIRC, it always holds s-rcu when write guest page and set dirty bit,
that mean the dirty page is logged either in the old dirty_bitmap or in the
current memslot->dirty_bitmap. Yes?

--
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/