Re: Fatal crash on xen4.2 HVM + qemu-xen dm + NFS

[Alex Bligh <alex@alex.org.uk>]

Konrad / Stefano,

Any update here?

I can't help but think a crashed dom0 and guaranteed domU corruption is
less bad than a theoretical data loss on a crash (not that we know
that theoretical possibility exists yet).

I'm currently using this trivial patch
 https://github.com/abligh/qemu-upstream-4.2-testing-livemigrate/commit/a7d72
96aebc21af15074f3bf64c5c6795ca05f16

Alex


--On 5 February 2013 15:40:33 +0000 Alex Bligh <alex@alex.org.uk> wrote:

> Konrad / Stefano,
>
> Any movement / ideas on this one?
>
> Alex
>
> --On 25 January 2013 11:28:31 +0000 Alex Bligh <alex@alex.org.uk> wrote:
>
>> Konrad,
>>
>> --On 23 January 2013 16:29:20 +0000 Stefano Stabellini
>> <stefano.stabellini@eu.citrix.com> wrote:
>>
>>>> diff --git a/hw/xen_disk.c b/hw/xen_disk.c
>>>> index a402ac8..1c3a6f5 100644
>>>> --- a/hw/xen_disk.c
>>>> +++ b/hw/xen_disk.c
>>>> @@ -603,7 +603,7 @@ static int blk_init(struct XenDevice *xendev)
>>>>      }
>>>>
>>>>      /* read-only ? */
>>>> -    qflags = BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NATIVE_AIO;
>>>> +    qflags = /* BDRV_O_NOCACHE | */ BDRV_O_CACHE_WB |
>>>> BDRV_O_NATIVE_AIO; if (strcmp(blkdev->mode, "w") == 0) {
>>>>          qflags |= BDRV_O_RDWR;
>>>>      } else {
>>>
>>> Before going for something like that I would like a confirmation from
>>> Konrad about blkfront behavior regarding barriers and
>>> BLKIF_OP_FLUSH_DISKCACHE. I certainly don't want to risk data
>>> corruptions.
>>
>> Any ideas?
>>
>>
>> A slightly prettier patch would look like the one pasted
>> below (not sent with git-sendemail so beware whitespace issues).
>>
>> --
>> Alex Bligh
>>
>> commit a7d7296aebc21af15074f3bf64c5c6795ca05f16
>> Author: Alex Bligh <alex@alex.org.uk>
>> Date:   Thu Jan 24 09:41:34 2013 +0000
>>
>>     Disable use of O_DIRECT by default as it results in crashes.
>>
>>     See:
>>       http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html
>>     for more details.
>>
>> diff --git a/hw/xen_disk.c b/hw/xen_disk.c
>> index a402ac8..a618d8d 100644
>> --- a/hw/xen_disk.c
>> +++ b/hw/xen_disk.c
>> @@ -45,6 +45,8 @@ static int batch_maps   = 0;
>>
>>  static int max_requests = 32;
>>
>> +static int use_o_direct = 0;
>> +
>>  /* ------------------------------------------------------------- */
>>
>>  # define BLOCK_SIZE  512
>> @@ -603,7 +605,7 @@ static int blk_init(struct XenDevice *xendev)
>>      }
>>
>>      /* read-only ? */
>> -    qflags = BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NATIVE_AIO;
>> +    qflags = (use_o_direct?BDRV_O_NOCACHE:0) | BDRV_O_CACHE_WB |
>> BDRV_O_NATIVE_AIO;
>>      if (strcmp(blkdev->mode, "w") == 0) {
>>          qflags |= BDRV_O_RDWR;
>>      } else {
>>
>>
>>
>
>
>
> --
> Alex Bligh
>
>



-- 
Alex Bligh