Re: [Xen-devel] [PATCHv2] 1/3] libxc: prefer using privcmd character device

[Doug Goldstein <cardoe@xxxxxxxxxx>]

On 12/1/15 5:46 AM, Ian Campbell wrote:
> On Tue, 2015-11-24 at 14:14 -0600, Doug Goldstein wrote:
>> Prefer using the character device over the proc file if the character
>> device exists. This follows similar conversions of xenbus to avoid
>> issues with FMODE_ATOMIC_POS added in Linux 3.14 and newer.
>>
>> CC: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
>> CC: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>> CC: Ian Campbell <ian.campbell@xxxxxxxxxx>
>> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
>> Signed-off-by: Doug Goldstein <cardoe@xxxxxxxxxx>
>> ---
>>  tools/libxc/xc_linux_osdep.c | 9 ++++++++-
>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/libxc/xc_linux_osdep.c b/tools/libxc/xc_linux_osdep.c
>> index 76c55ff..c078b3d 100644
>> --- a/tools/libxc/xc_linux_osdep.c
>> +++ b/tools/libxc/xc_linux_osdep.c
>> @@ -46,7 +46,14 @@
>>  static xc_osdep_handle linux_privcmd_open(xc_interface *xch)
>>  {
>>      int flags, saved_errno;
>> -    int fd = open("/proc/xen/privcmd", O_RDWR);
>> +    int fd = open("/dev/xen/privcmd", O_RDWR); /* prefer this newer
>> interface */
>> +
>> +    if ( fd == -1 && ( errno == ENOENT || errno == ENXIO ||
>> +                       errno == ENODEV || errno == EACCES ))
> 
> This adds EACCESS to the set Ian suggested would be tolerable in his reply
> to v1. I'm leaning towards thinking that if the device is present but not
> openable by the current user then that's a system configuration error which
> should be reported.
> 
> Anyone want to argue otherwise?
> 

I'll drop EACCES. I was just trying to be proactive for another possible
error.

-- 
Doug Goldstein

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