Re: raw disks no longer work in latest kvm (kvm-88 was fine)

[Avi Kivity <avi@redhat.com>]

On 03/07/2010 07:11 PM, Antoine Martin wrote:
>>
>> the problem happens right at startup, it can't read _anything_
>> at all from the disk.  In my case, the problem is intermittent
>> and happens under high load only, hence the big difference.
>>
>> But anyway, this is something which should be easy to find
>> out.  Run kvm under `strace -f' and see how it opens the
>>    device, or find out with lsof what filedescriptor corresponds
>> to the file in question (in running kvm instance) and see
>> flags in /proc/$kvm_pid/fdinfo/$fdnum.
> ...
> [...]
> stat("./vm/var_fs", {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 41), 
> ...}) = 0
> open("./vm/var_fs", O_RDWR|O_DIRECT|O_CLOEXEC) = 12
> lseek(12, 0, SEEK_END)      = 1321851815424
> [..]
> So it opens it the device without problems.
>
> The only things that stands out is this before the "read failed" message:
> [pid  9098] lseek(12, 0, SEEK_END)      = 1321851815424
> [pid  9121] pread(12, 0x7fa50a0e47d0, 2048, 0) = -1 EINVAL (Invalid 
> argument)
>

The buffer is unaligned here, yet the file was opened with O_DIRECT 
(cache=none).  This is strange, since alignment is not related to disk size.

-- 
error compiling committee.c: too many arguments to function