Re: [Xen-devel] [PATCH] linux_gntshr_munmap: munmap takes a length, not a page count

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 03/09/14 15:31, Ian Campbell wrote:
> On Wed, 2014-09-03 at 15:21 +0100, David Vrabel wrote:
>> On 03/09/14 15:17, Ian Campbell wrote:
>>> On Wed, 2014-09-03 at 15:15 +0100, David Vrabel wrote:
>>>> On 03/09/14 15:01, Ian Campbell wrote:
>>>>> On Mon, 2014-09-01 at 13:16 +0100, David Scott wrote:
>>>>>> This fixes a bug where if a client shares more than 1 page, the
>>>>>> munmap call fails to clean up everything. A process which does
>>>>>> a lot of sharing and unsharing can run out of resources.
>>>>> The doc comment on xc_gntshr_munmap does say count is in pages, so your
>>>>> change is correct but all of the in tree callers seem to pass a number
>>>>> of bytes not a number of pages. i.e. everything in tools/libvchan passes
>>>>> n*PAGE_SIZE.
>>>>>
>>>>> So I don't think this change is complete without also updating those.
>>>> Would the corrent non-ABI/API-breaking fix be to just update the
>>>> documentation?
>>> libxc doesn't have a stable API or ABI.
>> xc_gntshr_*() really should be part of a separate libxc-for-domu that
>> does have a stable ABI.
> This hadn't occurred to me, but yes, this does sound sensible.

Currently, all domU event and grant operations require libxc, including
the use of libxenstore.

I have raised this before, and believe there is a line item defered
until 4.6 to cleave libxc into several pieces, to avoid needing to put
libxc into all domUs to use the xenstore-* binaries.  libxenevent and
libxengrant seem like plausible library names.

~Andrew

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