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Re: [Xen-devel] [help] problem with `tools/xenstore/xs.c: xs_talkv()`

On Fri, 2013-01-04 at 11:38 +0000, éç wrote:
> On Fri, Jan 4, 2013 at 5:17 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx>
> wrote:
>         On Fri, 2013-01-04 at 03:55 +0000, éç wrote:
>         >
>         >     I looked into the functions for logging, in this case,
>          `3 = No
>         > such process` was from `errno` and the `
>         HYPERVISOR_event_channel_op
>         > failed: -1 ` was from hypervisor-level
>         > error(src/xen/common/event_channel.c).
>         > In my option, that's to say, error number of -1 was caused
>         by
>         > hypervisor; but what was the error number of 3 caused by,
>          dom0?
>         > Do both the two error numbers refer to the description
>         defined in
>         > errno.h or else hypervisor has its own error description?
>         This is just the usual Unix idiom where system calls (and by
>         extension
>         the ioctl used to make hypercalls) fail by returning -1 (which
>         has no
>         particular meaning other than "an error occurred") and set
>         errno to
>         something more specific (3 in this case, indicating ESRCH).
>         Please see the errno(3) man page.
>         Ian.
> Does the xen hypervisor set the errno to something specific when xen
> encounter an error?

No, errno handling is a function of the libc. Please use google to
lookup how system calls and errno etc work on a Linux system.

> Where are the hypervisor error descriptors and dom0 error descriptors
>  defined respectively?

Did you try grepping for them?

The Xen ones are in the Xen source tree. The dom0 ones are in the Linux
(or your dom0 kernel) source tree. I believe the Xen ones are a subset
of the Linux ones and that the numbers are consistent.


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