Re: [Xen-devel] [PATCH V2] tools/libxc, xen/x86: Added xc_set_mem_access_multi()

[Julien Grall <julien.grall@xxxxxxx>]

On 02/09/16 14:22, Razvan Cojocaru wrote:
> On 09/02/2016 04:17 PM, Julien Grall wrote:
>> Hello Razvan,
> 
> Hello Julien, thanks for the email!
> 
>> On 02/09/16 09:51, Razvan Cojocaru wrote:
>>> Currently it is only possible to set mem_access restrictions only for
>>> a contiguous range of GFNs (or, as a particular case, for a single GFN).
>>> This patch introduces a new libxc function taking an array of GFNs.
>>> The alternative would be to set each page in turn, using a userspace-HV
>>> roundtrip for each call, and triggering a TLB flush per page set.
>>>
>>> Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
>>>
>>> ---
>>> Changes since V1 / RFC:
>>>  - Renamed xc_set_mem_access_sparse() to xc_set_mem_access_multi(),
>>>    and XENMEM_access_op_set_access_sparse to
>>>    XENMEM_access_op_set_access_multi.
>>>  - Renamed the 'nr' parameter to 'size'.
>>>  - Wrapped long line in the implementation of xc_set_mem_access_multi().
>>>  - Factored out common code in _p2m_set_mem_access() (and modified
>>>    p2m_set_altp2m_mem_access() in the process, to take an unsigned
>>>    long argument instead of a gfn_t).
>>>  - Factored out xenmem_access_t to p2m_access_t conversion code in
>>>    p2m_xenmem_access_to_p2m_access().
>>>  - Added hypercall continuation support.
>>>  - Added compat translation support.
>>>  - No longer allocating buffers (now using copy_from_guest_offset()).
>>>  - Added support for setting an array of access restrictions, as
>>>    suggested by Tamas Lengyel.
>>>  - This patch incorporates Jan Beulich's "memory: fix compat handling
>>>    of XENMEM_access_op".
>>> ---
>>>  tools/libxc/include/xenctrl.h |   4 ++
>>>  tools/libxc/xc_mem_access.c   |  38 ++++++++++
>>>  xen/arch/x86/mm/p2m.c         | 161
>>> ++++++++++++++++++++++++++++++++----------
>>>  xen/common/compat/memory.c    |  24 +++++--
>>>  xen/common/mem_access.c       |  11 +++
>>>  xen/include/public/memory.h   |  14 +++-
>>>  xen/include/xen/p2m-common.h  |   6 ++
>>
>> p2m-common.h contains prototype common between ARM and x86. I would have
>> expected to see a change in the ARM port because of that.
> 
> The only change to p2m-common.h is the addition of a single function,
> p2m_set_mem_access_multi(). As long as the ARM bits don't make use of
> it, there's nothing to modify there.

p2m_set_mem_access_multi is called from common code. If you had tried
to build Xen on ARM you would have noticed a compilation error:

prelink.o: In function `mem_access_memop':
/local/home/julieng/works/xen/xen/common/mem_access.c:80: undefined reference 
to `p2m_set_mem_access_multi'
aarch64-linux-gnu-ld: /local/home/julieng/works/xen/xen/.xen-syms.0: hidden 
symbol `p2m_set_mem_access_multi' isn't defined

Regards,

-- 
Julien Grall

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