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From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Wei Wang <wei.w.wang@intel.com>,
	virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
	linux-mm@kvack.org, mst@redhat.com, mhocko@kernel.org,
	akpm@linux-foundation.org, dgilbert@redhat.com
Cc: torvalds@linux-foundation.org, pbonzini@redhat.com,
	liliang.opensource@gmail.com, yang.zhang.wz@gmail.com,
	quan.xu0@gmail.com, nilal@redhat.com, riel@redhat.com,
	peterx@redhat.com, quintela@redhat.com,
	Halil Pasic <pasic@linux.ibm.com>,
	Cornelia Huck <cohuck@redhat.com>
Subject: Re: [PATCH v37 0/3] Virtio-balloon: support free page reporting
Date: Thu, 27 Dec 2018 13:17:20 +0100	[thread overview]
Message-ID: <e79b5c3d-aa89-6b99-00b1-c92c85fe214c@de.ibm.com> (raw)
In-Reply-To: <de167161-b586-6aee-d6a5-a90d47bbe1d4@de.ibm.com>



On 27.12.2018 12:59, Christian Borntraeger wrote:
> On 27.12.2018 12:31, Christian Borntraeger wrote:
>> This patch triggers random crashes in the guest kernel on s390 early during boot.
>> No migration and no setting of the balloon is involved.
>>
> 
> Adding Conny and Halil,
> 
> As the QEMU provides no PAGE_HINT feature yet, this quick hack makes the
> guest boot fine again:
> 
> 
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 728ecd1eea305..aa2e1864c5736 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -492,7 +492,7 @@ static int init_vqs(struct virtio_balloon *vb)
>                 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
>         }
>  
> -       err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
> +       err = vb->vdev->config->find_vqs(vb->vdev, 3, //VIRTIO_BALLOON_VQ_MAX,
>                                          vqs, callbacks, names, NULL, NULL);
>         if (err)
>                 return err;
> 
> 
> To me it looks like that virtio_ccw_find_vqs will abort if any of the virtqueues 
> that it is been asked for does not exist (including the earlier ones).
> 

This "hack" makes the random crashes go away, but the balloon interface itself
does not work. (setting the value to anything will hang the guest). 
As patch 1 also modifies the main path, there seem to be additional issues, maybe
endianess

Looking at things like

+		vb->cmd_id_received = VIRTIO_BALLOON_CMD_ID_STOP;
+		vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
+						  VIRTIO_BALLOON_CMD_ID_STOP);
+		vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
+						  VIRTIO_BALLOON_CMD_ID_STOP);


Why is cmd_id_received not using cpu_to_virtio32?


  reply	other threads:[~2018-12-27 12:17 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-27  1:32 Wei Wang
2018-08-27  1:32 ` [PATCH v37 1/3] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT Wei Wang
2018-12-27 12:03   ` Christian Borntraeger
2018-12-28  3:12     ` Wei Wang
2018-12-28  8:03       ` Christian Borntraeger
2018-08-27  1:32 ` [PATCH v37 2/3] mm/page_poison: expose page_poisoning_enabled to kernel modules Wei Wang
2018-08-27  1:32 ` [PATCH v37 3/3] virtio-balloon: VIRTIO_BALLOON_F_PAGE_POISON Wei Wang
2018-10-25  0:58 ` [PATCH v37 0/3] Virtio-balloon: support free page reporting Michael S. Tsirkin
2018-10-25 10:18   ` Wei Wang
2018-12-27 11:31 ` Christian Borntraeger
2018-12-27 11:59   ` Christian Borntraeger
2018-12-27 12:17     ` Christian Borntraeger [this message]
2018-12-28  6:41       ` Wei Wang

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