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Re: [Xen-devel] [PATCHv3] QEMU(upstream): Disable xen's use of O_DIRECT by default as it results in crashes.

On 11/03/13 14:02, Alex Bligh wrote:

--On 8 March 2013 12:54:16 +0000 George Dunlap
<George.Dunlap@xxxxxxxxxxxxx> wrote:

On Fri, Mar 8, 2013 at 11:40 AM, Alex Bligh <alex@xxxxxxxxxxx> wrote:
Due to what is almost certainly a kernel bug, writes with
O_DIRECT may continue to reference the page after the write
has been marked as completed, particularly in the case of
TCP retransmit. In other scenarios, this "merely" risks
data corruption on the write, but with Xen pages from domU
are only transiently mapped into dom0's memory, resulting
in kernel panics when they are subsequently accessed.

This brings PV devices in line with emulated devices. Removing
O_DIRECT is safe as barrier operations are now correctly passed
Not qualified to comment on the technical merits of the patch, but re
the commit message:

Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Any further thoughts on this one?

I believe that Stefano is the person to commit it, but he's on holiday for two weeks.


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