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: Mon, 04 Dec 2017 13:39:28 +0800 [thread overview]
Message-ID: <5A24DF90.5070401@intel.com> (raw)
In-Reply-To: <20171201173951-mutt-send-email-mst@kernel.org>
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.
I think the 0-filled pages still need to be sent. If the host on the
destination doesn't use PAGE_POISONING_ZERO, then the pages it offers to
the guest on the destination may have non-0 values.
>
> 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.
>
>
OK, but I think we would need two 32-bit config registers:
__u32 page_poison_val; // stores the PAGE_POISON VALUE, but it couldn't
indicate if page poisoning is in use
__u32 special_features; // set bit 0 to indicate page poisoning is in use
#define VIRTIO_BALLOON_SF_PAGE_POISON (1 << 0)
Best,
Wei
next prev parent reply other threads:[~2017-12-04 5:37 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 [this message]
2017-12-11 6:38 ` Wei Wang
2017-12-11 13:24 ` Michael S. Tsirkin
2017-12-12 12:21 ` Wei Wang
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