Re: [Xen-devel] HVM domain with write caching going on somewhere to disk

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 8/11/07 11:08, "James Harper" <james.harper@xxxxxxxxxxxxxxxx> wrote:

>> No, it's trickier than that. Blkback sends I/O requests direct into
> the
>> block subsystem, bypassing the buffer cache. You can see there's
> potential
>> for confusion therefore!
> 
> Ah yes. That would probably do it. So I need to make sure that the
> buffer cache is flushed (eg async writes in qemu?)... or maybe get qemu
> to talk direct to the block subsystem in the same way... any
> suggestions? I've already butchered ioemu to get this working so far
> (changed the PCI ID's of the IDE interface so Windows won't detect it)
> so I'm not afraid of doing more of it :)

Qemu-dm should probably be specifying O_DIRECT when it opens guest storage
volumes. There was discussion about this quite some time ago, but I don't
think any patch was ever floated.

 -- Keir



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