From: Wei Wang <wei.w.wang@intel.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org,
qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org,
kvm@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org,
akpm@linux-foundation.org, mawilcox@microsoft.com,
david@redhat.com, penguin-kernel@I-love.SAKURA.ne.jp,
cornelia.huck@de.ibm.com, mgorman@techsingularity.net,
aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com,
willy@infradead.org, liliang.opensource@gmail.com,
yang.zhang.wz@gmail.com, quan.xu@aliyun.com, nilal@redhat.com,
riel@redhat.com
Subject: Re: [PATCH v18 10/10] virtio-balloon: don't report free pages when page poisoning is enabled
Date: Tue, 12 Dec 2017 20:21:31 +0800 [thread overview]
Message-ID: <5A2FC9CB.7030508@intel.com> (raw)
In-Reply-To: <20171211152258-mutt-send-email-mst@kernel.org>
On 12/11/2017 09:24 PM, Michael S. Tsirkin wrote:
> On Mon, Dec 11, 2017 at 02:38:45PM +0800, Wei Wang wrote:
>> On 12/01/2017 11:49 PM, Michael S. Tsirkin wrote:
>>> On Wed, Nov 29, 2017 at 09:55:26PM +0800, Wei Wang wrote:
>>>> The guest free pages should not be discarded by the live migration thread
>>>> when page poisoning is enabled with PAGE_POISONING_NO_SANITY=n, because
>>>> skipping the transfer of such poisoned free pages will trigger false
>>>> positive when new pages are allocated and checked on the destination.
>>>> This patch skips the reporting of free pages in the above case.
>>>>
>>>> Reported-by: Michael S. Tsirkin <mst@redhat.com>
>>>> Signed-off-by: Wei Wang <wei.w.wang@intel.com>
>>>> Cc: Michal Hocko <mhocko@suse.com>
>>>> ---
>>>> drivers/virtio/virtio_balloon.c | 4 +++-
>>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
>>>> index 035bd3a..6ac4cff 100644
>>>> --- a/drivers/virtio/virtio_balloon.c
>>>> +++ b/drivers/virtio/virtio_balloon.c
>>>> @@ -652,7 +652,9 @@ static void report_free_page(struct work_struct *work)
>>>> /* Start by sending the obtained cmd id to the host with an outbuf */
>>>> send_one_desc(vb, vb->free_page_vq, virt_to_phys(&vb->start_cmd_id),
>>>> sizeof(uint32_t), false, true, false);
>>>> - walk_free_mem_block(vb, 0, &virtio_balloon_send_free_pages);
>>>> + if (!(page_poisoning_enabled() &&
>>>> + !IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY)))
>>>> + walk_free_mem_block(vb, 0, &virtio_balloon_send_free_pages);
>>>> /*
>>>> * End by sending the stop id to the host with an outbuf. Use the
>>>> * non-batching mode here to trigger a kick after adding the stop id.
>>> PAGE_POISONING_ZERO is actually OK.
>>>
>>> But I really would prefer it that we still send pages to host,
>>> otherwise debugging becomes much harder.
>>>
>>> And it does not have to be completely useless, even though
>>> you can not discard them as they would be zero-filled then.
>>>
>>> How about a config field telling host what should be there in the free
>>> pages? This way even though host can not discard them, host can send
>>> them out without reading them, still a win.
>>>
>>>
>> Since this poison value comes with the free page reporting feature, how
>> about sending the poison value via the free_page_vq, along with the cmd id
>> in the outbuf? That is, use the following interface:
>>
>> struct virtio_balloon_free_page_vq_hdr {
>> bool page_poisoning;
>> __virtio32 poison_value;
>> __virtio32 cmd_id;
>> }
> Can we put the value in config space instead?
>
>> We need "bool page_poisoning" because "poison_value=0" doesn't tell whether
>> page poising is in use by the guest.
> Can we use a feature bit for this?
>
>> PAGE_POISONING_ZERO sets
>> "page_poisoning=true, poisoning_value=0", and the host will send the
>> 0-filled pages to the destination (if not sending 0-filled pages, the
>> destination host would offer non-zero pages to the guest)
> Why would it? Linux zeroes all pages on alloc.
>
Thanks, that is the case. I think we don't need a feature bit then.
Please have a check the v19 patches.
Best,
Wei
prev parent reply other threads:[~2017-12-12 12:19 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-29 13:55 [PATCH v18 00/10] Virtio-balloon Enhancement Wei Wang
2017-11-29 13:55 ` [PATCH v18 01/10] idr: add #include <linux/bug.h> Wei Wang
2017-11-30 0:58 ` Matthew Wilcox
2017-11-30 7:07 ` Michal Hocko
2017-11-30 21:49 ` Andrew Morton
2017-11-29 13:55 ` [PATCH v18 02/10] radix tree test suite: remove ARRAY_SIZE to avoid redefinition Wei Wang
2017-11-29 13:55 ` [PATCH v18 03/10] xbitmap: Introduce xbitmap Wei Wang
2017-11-29 13:55 ` [PATCH v18 04/10] xbitmap: potential improvement Wei Wang
2017-11-29 13:55 ` [PATCH v18 05/10] xbitmap: add more operations Wei Wang
2017-11-30 10:34 ` Tetsuo Handa
2017-11-30 13:35 ` Tetsuo Handa
2017-11-30 14:39 ` Matthew Wilcox
2017-12-03 1:44 ` Tetsuo Handa
2017-12-01 8:02 ` Wei Wang
2017-12-01 13:02 ` Tetsuo Handa
2017-12-01 14:13 ` Matthew Wilcox
2017-12-01 15:09 ` Wang, Wei W
2017-12-01 17:25 ` Matthew Wilcox
2017-12-03 1:50 ` Tetsuo Handa
2017-12-07 12:01 ` Wei Wang
2017-12-07 15:41 ` Michael S. Tsirkin
2017-11-29 13:55 ` [PATCH v18 06/10] virtio_ring: add a new API, virtqueue_add_one_desc Wei Wang
2017-11-30 19:38 ` Michael S. Tsirkin
2017-12-01 8:06 ` Wei Wang
2017-11-29 13:55 ` [PATCH v18 07/10] virtio-balloon: VIRTIO_BALLOON_F_SG Wei Wang
2017-11-30 10:35 ` Tetsuo Handa
2017-11-30 16:25 ` Wang, Wei W
2017-12-01 15:38 ` Michael S. Tsirkin
2017-12-04 3:46 ` Wei Wang
2017-11-29 13:55 ` [PATCH v18 08/10] mm: support reporting free page blocks Wei Wang
2017-11-29 13:55 ` [PATCH v18 09/10] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ Wei Wang
2017-11-29 13:55 ` [PATCH v18 10/10] virtio-balloon: don't report free pages when page poisoning is enabled Wei Wang
2017-12-01 15:49 ` Michael S. Tsirkin
2017-12-04 5:39 ` Wei Wang
2017-12-11 6:38 ` Wei Wang
2017-12-11 13:24 ` Michael S. Tsirkin
2017-12-12 12:21 ` Wei Wang [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5A2FC9CB.7030508@intel.com \
--to=wei.w.wang@intel.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=amit.shah@redhat.com \
--cc=cornelia.huck@de.ibm.com \
--cc=david@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=liliang.opensource@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mawilcox@microsoft.com \
--cc=mgorman@techsingularity.net \
--cc=mhocko@kernel.org \
--cc=mst@redhat.com \
--cc=nilal@redhat.com \
--cc=pbonzini@redhat.com \
--cc=penguin-kernel@I-love.SAKURA.ne.jp \
--cc=qemu-devel@nongnu.org \
--cc=quan.xu@aliyun.com \
--cc=riel@redhat.com \
--cc=virtio-dev@lists.oasis-open.org \
--cc=virtualization@lists.linux-foundation.org \
--cc=willy@infradead.org \
--cc=yang.zhang.wz@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).