Re: AW: [Xen-devel] VHD BUG in xen4.0 when install windows2008

[yingbin wang <yingbin.wangyb@xxxxxxxxx>]

hi,
had you created the patch to make tapdisk run the device queue synchronously?
if yes, could you tell me how to get it?

thanks
wyb

2010/5/10 Daniel Stodden <daniel.stodden@xxxxxxxxxx>:
> On Sun, 2010-05-09 at 15:03 -0400, Heiko Wundram wrote:
>> As I'm seeing a similar behavior of tapdisk2 (see my recent posts to 
>> xen-users, especially "blktap2, also broken in current pv_ops 
>> stable-2.6.32.x?"), I can confirm that at least in my testing (I've done 
>> some more over the weekend, re. that message), this is indeed an 
>> "SMP-related" problem, but only for HVM-64bit domains.
>>
>> What I can basically say is that:
>>
>> 1) Uni/Multi/32-bit/64-bit PV domains run properly.
>> 1) Uni-VCPU, 32-bit HVM domains run properly.
>> 2) Multi-VCPU, 32-bit HVM domains run properly.
>> 3) Uni-VCPU, 64-bit HVM domains run properly.
>> 4) Multi-VCPU, 64-bit HVM domains cause tapdisk2 to segfault, sometimes, 
>> under heavy I/O, and if that happens, causes the Dom0-kernel to freeze/lock 
>> up, Bug, and/or all other kinds of undefined behavior, where I really 
>> haven't made out a pattern yet.
>>
>> Interestingly, these errors do not happen when using the "normal" 
>> blkback-driver, and I'm very positive (at least that's what happened during 
>> my testing) that it's specific to Multi-VCPU, 64-bit HVM domains that the 
>> crash occurs, independent of the number of VCPUs bound to Dom0.
>
> Okay, one thing which was going to happen soon is a patch to make
> tapdisk run the device queue synchronously. From your description I'm
> just not very convinced that this resolves such issues as well. Looks
> like it needs some 64 bit testing beforehand.
>
> Thanks for the hints. Does HVM up there mean it's rather triggered by
> qemu alone? Were you running pv drivers?
>
> Cheers,
> Daniel
>
>
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