On 05/23/2010 09:43 PM, Antoine Martin wrote:
On 05/23/2010 09:18 PM, Avi Kivity wrote:
On 05/23/2010 05:07 PM, Antoine Martin wrote:
On 05/23/2010 06:57 PM, Avi Kivity wrote:
On 05/23/2010 11:53 AM, Antoine Martin wrote:
I'm not: 64-bit host and 64-bit guest.
Just to be sure, I've tested that patch and still no joy:
/dev/vdc: read failed after 0 of 512 at 0: Input/output error
/dev/vdc: read failed after 0 of 512 at 0: Input/output error
/dev/vdc: read failed after 0 of 2048 at 0: Input/output error
pread is still broken on this big raw disk.
Can you summarize your environment and reproducer again? The
thread is so long it is difficult to understand exactly what you
are testing.
Sure thing:
Description of the problem:
A guest tries to mount a large raw partition (1.5TB /dev/sda9 in my
case), this fails with pread enabled, works with it disabled.
Did you mean: preadv?
Yes, here's what makes it work ok (as suggested by Christoph earlier
in the thread) in posix-aio-compat.c:
#undef CONFIG_PREADV
#ifdef CONFIG_PREADV
static int preadv_present = 1;
#else
static int preadv_present = 0;
#endif
What has been tested:
Host has had 2.6.31.x and now 2.6.34 - with no improvement.
Guest has had numerous kernel versions and patches applied for
testing (from 2.6.31.x to 2.6.34) - none made any difference.
(although the recent patch stopped the large partition from getting
corrupted by the merged requests bug.. yay!)
It was once thought that glibc needed to be rebuilt against newer
kernel headers, done that too, and rebuilt qemu-kvm afterwards. (was
2.6.28 then 2.6.31 and now 2.6.33)
What has been reported: straces, kernel error messages as above.
Here is the qemu command line (sanitized - removed the virtual disks
which work fine and network config):
qemu -clock dynticks -m 256 -L ./ -kernel ./bzImage-2.6.34-aio
-append "root=/dev/vda" -nographic -drive
file=/dev/sda9,if=virtio,cache=none
Let me know if you need any other details. I can also arrange ssh
access to the system if needed.
And: 64-bit host kernel, 64-bit host userspace, yes?
Yes. (and 64-bit guest/userspace too)
Does aio=native help?
It does indeed!
How about if=ide?
Will test with another kernel and report back (this one doesn't have
any non-virtio drivers)
That also works fine.
I guess this tells you that the problem is confined to
raw-disk+virtio+aio-threaded
I'm switching all my VMs to aio=native, but feel free to send patches if
you want me to re-test aio=threaded
Thanks
Antoine
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