From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH 06/15] memory: use refcnt to manage
	MemoryRegion
Date: Sun, 12 Aug 2012 11:43:48 +0300
Message-ID: <50276CC4.6040201@redhat.com>
References: <1344407156-25562-1-git-send-email-qemulist@gmail.com>
	<1344407156-25562-7-git-send-email-qemulist@gmail.com>
	<50222F54.4080108@redhat.com>
	<CAJnKYQmsAZE5VD3oXvA3NfLqVc-Z-98KT+UiL0g8KPBx=0avkg@mail.gmail.com>
	<5023771F.5030007@redhat.com>
	<CAJnKYQm5VsJU18M3FVJK=GJR7wz796PyDFqR8_8tdvaR=bTF_w@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Cc: kvm@vger.kernel.org, Jan Kiszka <jan.kiszka@siemens.com>,
	Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org,
	Blue Swirl <blauwirbel@gmail.com>, Anthony Liguori <anthony@codemonkey.ws>,
	Stefan Hajnoczi <stefanha@gmail.com>, Paolo Bonzini <pbonzini@redhat.com>,
	=?ISO-8859-1?Q?Andreas_F=E4rber?= <afaerber@suse.de>
To: liu ping fan <qemulist@gmail.com>
Return-path: <qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org>
In-Reply-To: <CAJnKYQm5VsJU18M3FVJK=GJR7wz796PyDFqR8_8tdvaR=bTF_w@mail.gmail.com>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org
Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org
List-Id: kvm.vger.kernel.org

On 08/10/2012 09:44 AM, liu ping fan wrote:
>>> In the previous discussion, you have suggest add dev->ref++ in
>>> core_region_add.  But I think, if we can move it to higher layer --
>>> memory_region_{add,del}_subregion, so we can avoid to duplicate do
>>> this in other xx_region_add.
>>
>> Why would other memory listeners be impacted?  They all operate under
>> the big qemu lock.  If they start using devices outside the lock, then
>> they need to take a reference.
>>
> Yes, if unplug path in the protection of big lock.
> And just one extra question, for ram-unplug scene, how do we protect from:
>   updater:  ram-unplug -->qemu free() --> brk() invalidate this vaddr interval
>   reader:  vhost-thread copy data from the interval
> I guess something like lock/ref used by them, but can not find such
> mechanism in vhost_set_memory() to protect the scene against
> vhost_worker()

VHOST_SET_MEM_TABLE uses synchronize_srcu() to ensure no readers are
active before returning.


-- 
error compiling committee.c: too many arguments to function