Re: [PATCHv2 0/2] xen/privcmd: support for paged-out frames

[David Vrabel <david.vrabel@citrix.com>]

On 29/08/12 17:23, Ian Campbell wrote:
> On Wed, 2012-08-29 at 14:15 +0100, David Vrabel wrote:
>> This series is a straight forward-port of some functionality from
>> classic kernels to support Xen hosts that do paging of guests.
>>
>> This isn't functionality the XenServer makes use of so I've not tested
>> these with paging in use.
>>
>> Changes since v1:
>>
>> - Don't change PRIVCMD_MMAPBATCH (except to #define a constant for the
>>   error).  It's broken and not really fixable sensibly and libxc will
>>   use V2 if it is available.
>> - Return -ENOENT if all failures were -ENOENT.
> 
> Is this behaviour a requirement from something?

It's the behaviour libxc is expecting.  It doesn't retry unless errno ==
ENOENT.

> Usually hypercalls of this type return a global error only if something
> went wrong with the general mechanics of the hypercall (e.g. faults
> reading arguments etc) and leave reporting of the individual failures of
> subops to the op specific field, even if all the subops fail in the same
> way.

I didn't design this interface...  Feel free to propose (and implement)
an alternate MMAPBATCH_V3 interface.

David