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From: Julien Grall <julien.grall@arm.com>
To: Jan Beulich <jbeulich@suse.com>, wei.liu2@citrix.com
Cc: tim@xen.org, sstabellini@kernel.org, George.Dunlap@eu.citrix.com,
	andrew.cooper3@citrix.com, ian.jackson@eu.citrix.com,
	xen-devel@lists.xen.org
Subject: Re: [PATCH v4 12/16] xen/mm: Switch common/memory.c to use typesafe MFN
Date: Wed, 14 Mar 2018 16:08:28 +0000	[thread overview]
Message-ID: <df498917-d692-ed87-bb53-c9d6f4546aab@arm.com> (raw)
In-Reply-To: <5AA6209E0200007800129BC1@prv-mh.provo.novell.com>

Hi Jan,

On 03/12/2018 06:39 AM, Jan Beulich wrote:
>>>> Julien Grall <julien.grall@arm.com> 03/11/18 8:44 PM >>>
>> On 03/09/2018 05:33 PM, Wei Liu wrote:
>>> On Mon, Mar 05, 2018 at 07:41:54AM -0700, Jan Beulich wrote:
>>>>>>> On 05.03.18 at 15:18, <julien.grall@arm.com> wrote:
>>>>> Also, do you have an opinion on Wei's suggestion:
>>>>>
>>>>> "What I meant was to make copy_{to,from}_guest* type-safe. I just feel it
>>>>> a bit strange you only created a wrapper for this file. I wonder why.
>>>>>
>>>>> Note I'm just asking question. That's not necessarily a good idea to
>>>>> turn them all in the end."
>>>>
>>>> Well, I didn't really understand what he's after (in the context of
>>>> this series) - copy_{to,from}_guest() don't take or return MFNs or
>>>> GFNs.
>>>>
>>>
>>> Fundamentally Julien's patch is to wrap around an existing API for this
>>> one file only. Why is this file special? Why not just make that class of
>>> APIs do what he wants?
>>>
>>> But that is going to be intrusive and a bit counter-intuitive.
>>
>> I have quickly looked at it. The major problem I can see is it is not
>> possible to generically define for any typesafe. Indeed, TYPE_SAFE(...)
>> cannot define new macro and, AFAICT, it is not feasible to define static
>> inline for copy_* helpers.
>>
>> So we would need to introduce macros for each typesafe by hand. I can
>> move copy_mfn_to_guest in xen/mm.h if people think it could be useful.
> 
> First of all - how often do we copy in/out individual MFNs? Not in many places,
> I think. Hence I'm afraid I continue to not see the value of such a construct,
> especially not as a wider-than-file-scope one.

I think you are right. Looking at the interface, we tend copy copy more 
often a GFN. We might want to provide an helper for typesafe GFN in the 
future.

Cheers.

-- 
Julien Grall

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  reply	other threads:[~2018-03-14 16:08 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-21 14:02 [PATCH v4 00/16] xen: Convert page_to_mfn and mfn_to_page to use typesafe MFN Julien Grall
2018-02-21 14:02 ` [PATCH v4 01/16] xen/tmem: Convert the file common/tmem_xen.c " Julien Grall
2018-02-21 14:02 ` [PATCH v4 02/16] xen/arm: setup: use maddr_to_mfn rather than _mfn(paddr_to_pfn(...)) Julien Grall
2018-02-21 14:02 ` [PATCH v4 03/16] xen/arm: mm: Use gaddr_to_gfn rather than _gfn(paddr_to_pfn(...)) Julien Grall
2018-02-21 14:02 ` [PATCH v4 04/16] xen/arm: mm: Remove unused M2P code Julien Grall
2018-02-21 14:02 ` [PATCH v4 05/16] xen/arm: mm: Remove unused relinquish_shared_pages Julien Grall
2018-02-21 14:02 ` [PATCH v4 06/16] xen/x86: Remove unused override of page_to_mfn/mfn_to_page Julien Grall
2018-03-01 11:20   ` George Dunlap
2018-03-02 14:42   ` Jan Beulich
2018-03-02 14:44     ` Julien Grall
2018-03-02 15:11       ` Jan Beulich
2018-03-05 13:29         ` Julien Grall
2018-02-21 14:02 ` [PATCH v4 07/16] xen/x86: mm: Switch x86/mm.c to use typesafe for virt_to_mfn Julien Grall
2018-03-02 14:45   ` Jan Beulich
2018-03-02 14:46     ` Julien Grall
2018-02-21 14:02 ` [PATCH v4 08/16] xen/mm: Drop the parameter mfn from populate_pt_range Julien Grall
2018-02-22 16:35   ` Wei Liu
2018-02-22 16:40     ` Julien Grall
2018-02-22 16:51       ` Wei Liu
2018-02-22 16:55         ` Julien Grall
2018-02-22 17:10           ` Wei Liu
2018-03-02 14:55           ` Jan Beulich
2018-03-05 13:43             ` Julien Grall
2018-03-05 14:00               ` Jan Beulich
2018-03-05 14:11                 ` Julien Grall
2018-03-05 14:38                   ` Jan Beulich
2018-03-09 17:29                     ` Wei Liu
2018-03-11 19:30                       ` Julien Grall
2018-03-12  6:36                       ` Jan Beulich
2018-03-14 15:22                         ` Julien Grall
2018-02-21 14:02 ` [PATCH v4 09/16] xen/pdx: Introduce helper to convert MFN <-> PDX Julien Grall
2018-02-22 16:39   ` Wei Liu
2018-02-21 14:02 ` [PATCH v4 10/16] xen/mm: Switch map_pages_to_xen to use MFN typesafe Julien Grall
2018-02-23  4:59   ` Tian, Kevin
2018-02-23 17:21   ` Wei Liu
2018-03-02 15:06   ` Jan Beulich
2018-03-02 15:08     ` Jan Beulich
2018-03-05 14:07     ` Julien Grall
2018-03-05 14:39       ` Jan Beulich
2018-03-05 14:44         ` Julien Grall
2018-02-21 14:02 ` [PATCH v4 11/16] xen/mm: Switch page_alloc.c to typesafe MFN Julien Grall
2018-02-23 17:21   ` Wei Liu
2018-03-02 15:18   ` Jan Beulich
2018-03-02 15:57     ` Julien Grall
2018-02-21 14:02 ` [PATCH v4 12/16] xen/mm: Switch common/memory.c to use " Julien Grall
2018-02-23 17:26   ` Wei Liu
2018-02-23 17:46     ` Julien Grall
2018-02-23 18:05       ` Wei Liu
2018-02-23 18:06         ` Julien Grall
2018-02-23 18:10           ` Wei Liu
2018-03-02 15:34   ` Jan Beulich
2018-03-05 14:18     ` Julien Grall
2018-03-05 14:41       ` Jan Beulich
2018-03-09 17:33         ` Wei Liu
2018-03-11 19:44           ` Julien Grall
2018-03-12  6:39             ` Jan Beulich
2018-03-14 16:08               ` Julien Grall [this message]
2018-02-21 14:02 ` [PATCH v4 13/16] xen/grant: Switch {create, replace}_grant_p2m_mapping to " Julien Grall
2018-02-23 17:29   ` Wei Liu
2018-03-02 15:38   ` Jan Beulich
2018-02-21 14:02 ` [PATCH v4 14/16] xen/grant: Switch common/grant_table.c to use " Julien Grall
2018-02-23 17:30   ` Wei Liu
2018-03-02 15:54   ` Jan Beulich
2018-03-02 15:59     ` Julien Grall
2018-03-02 16:12       ` Jan Beulich
2018-02-21 14:02 ` [PATCH v4 15/16] xen/x86: Switch mfn_to_page in x86_64/mm.c " Julien Grall
2018-03-02 15:57   ` Jan Beulich
2018-02-21 14:02 ` [PATCH v4 16/16] xen: Convert page_to_mfn and mfn_to_page " Julien Grall
2018-02-21 14:25   ` Razvan Cojocaru
2018-02-21 14:59   ` Paul Durrant
2018-02-21 23:20   ` Boris Ostrovsky
2018-02-23  4:59   ` Tian, Kevin
2018-02-23 17:31   ` Wei Liu
2018-03-02 16:08   ` Jan Beulich
2018-03-14 17:02     ` Julien Grall
2018-03-15  7:07       ` Jan Beulich

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