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From: "Jürgen Groß" <jgross@suse.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: linux-kernel@vger.kernel.org,
	Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
	David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Dan Carpenter <dan.carpenter@oracle.com>, Wei Liu <wl@xen.org>,
	Yan Yankovskyi <yyankovskyi@gmail.com>,
	dri-devel@lists.freedesktop.org, xen-devel@lists.xenproject.org,
	linux-mm@kvack.org, David Hildenbrand <david@redhat.com>,
	Michal Hocko <mhocko@kernel.org>,
	Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH v5 3/3] xen: add helpers to allocate unpopulated memory
Date: Fri, 4 Sep 2020 14:40:26 +0200	[thread overview]
Message-ID: <41905296-c157-938b-4953-19af3435c085@suse.com> (raw)
In-Reply-To: <20200904084229.GN753@Air-de-Roger>

On 04.09.20 10:42, Roger Pau Monné wrote:
> On Fri, Sep 04, 2020 at 09:00:18AM +0200, Jürgen Groß wrote:
>> On 03.09.20 18:38, Roger Pau Monné wrote:
>>> On Thu, Sep 03, 2020 at 05:30:07PM +0200, Jürgen Groß wrote:
>>>> On 01.09.20 10:33, Roger Pau Monne wrote:
>>>>> To be used in order to create foreign mappings. This is based on the
>>>>> ZONE_DEVICE facility which is used by persistent memory devices in
>>>>> order to create struct pages and kernel virtual mappings for the IOMEM
>>>>> areas of such devices. Note that on kernels without support for
>>>>> ZONE_DEVICE Xen will fallback to use ballooned pages in order to
>>>>> create foreign mappings.
>>>>>
>>>>> The newly added helpers use the same parameters as the existing
>>>>> {alloc/free}_xenballooned_pages functions, which allows for in-place
>>>>> replacement of the callers. Once a memory region has been added to be
>>>>> used as scratch mapping space it will no longer be released, and pages
>>>>> returned are kept in a linked list. This allows to have a buffer of
>>>>> pages and prevents resorting to frequent additions and removals of
>>>>> regions.
>>>>>
>>>>> If enabled (because ZONE_DEVICE is supported) the usage of the new
>>>>> functionality untangles Xen balloon and RAM hotplug from the usage of
>>>>> unpopulated physical memory ranges to map foreign pages, which is the
>>>>> correct thing to do in order to avoid mappings of foreign pages depend
>>>>> on memory hotplug.
>>>>>
>>>>> Note the driver is currently not enabled on Arm platforms because it
>>>>> would interfere with the identity mapping required on some platforms.
>>>>>
>>>>> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
>>>>
>>>> Sorry, I just got a build error for x86 32-bit build:
>>>>
>>>> WARNING: unmet direct dependencies detected for ZONE_DEVICE
>>>>     Depends on [n]: MEMORY_HOTPLUG [=n] && MEMORY_HOTREMOVE [=n] &&
>>>> SPARSEMEM_VMEMMAP [=n] && ARCH_HAS_PTE_DEVMAP [=n]
>>>>     Selected by [y]:
>>>>     - XEN_UNPOPULATED_ALLOC [=y] && XEN [=y] && X86 [=y]
>>>>     GEN     Makefile
>>>>     CC      kernel/bounds.s
>>>>     CALL    /home/gross/korg/src/scripts/atomic/check-atomics.sh
>>>>     UPD     include/generated/bounds.h
>>>>     CC      arch/x86/kernel/asm-offsets.s
>>>> In file included from /home/gross/korg/src/include/linux/mmzone.h:19:0,
>>>>                    from /home/gross/korg/src/include/linux/gfp.h:6,
>>>>                    from /home/gross/korg/src/include/linux/slab.h:15,
>>>>                    from /home/gross/korg/src/include/linux/crypto.h:19,
>>>>                    from /home/gross/korg/src/arch/x86/kernel/asm-offsets.c:9:
>>>> /home/gross/korg/src/include/linux/page-flags-layout.h:95:2: error: #error
>>>> "Not enough bits in page flags"
>>>>    #error "Not enough bits in page flags"
>>>>     ^~~~~
>>>> make[2]: *** [/home/gross/korg/src/scripts/Makefile.build:114:
>>>> arch/x86/kernel/asm-offsets.s] Error 1
>>>> make[1]: *** [/home/gross/korg/src/Makefile:1175: prepare0] Error 2
>>>> make[1]: Leaving directory '/home/gross/korg/x8632'
>>>> make: *** [Makefile:185: __sub-make] Error 2
>>>
>>> Sorry for this. I've tested a 32bit build but I think it was before
>>> the last Kconfig changes. I'm a little unsure how to solve this, as
>>> ZONE_DEVICE doesn't select the required options for it to run, but
>>> rather depends on them to be available.
>>>
>>> You can trigger something similar on x86-64 by doing:
>>>
>>> $ make ARCH=x86_64 xen.config
>>> Using .config as base
>>> Merging ./kernel/configs/xen.config
>>> Merging ./arch/x86/configs/xen.config
>>> #
>>> # merged configuration written to .config (needs make)
>>> #
>>> scripts/kconfig/conf  --olddefconfig Kconfig
>>>
>>> WARNING: unmet direct dependencies detected for ZONE_DEVICE
>>>     Depends on [n]: MEMORY_HOTPLUG [=y] && MEMORY_HOTREMOVE [=n] && SPARSEMEM_VMEMMAP [=y] && ARCH_HAS_PTE_DEVMAP [=y]
>>>     Selected by [y]:
>>>     - XEN_UNPOPULATED_ALLOC [=y] && XEN [=y] && X86_64 [=y]
>>> #
>>> # configuration written to .config
>>> #
>>>
>>> I think the only solution is to have XEN_UNPOPULATED_ALLOC depend on
>>> ZONE_DEVICE rather than select it?
>>
>> Yes, I think so.
>>
>> I've folded that in and now build is fine.
> 
> Thanks, I assume no further action is needed on my side.

Right.


Juergen


  reply	other threads:[~2020-09-04 12:41 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-01  8:33 [PATCH v5 0/3] xen/balloon: fixes for memory hotplug Roger Pau Monne
2020-09-01  8:33 ` [PATCH v5 1/3] xen/balloon: add header guard Roger Pau Monne
2020-09-01  8:33 ` [PATCH v5 2/3] memremap: rename MEMORY_DEVICE_DEVDAX to MEMORY_DEVICE_GENERIC Roger Pau Monne
2020-09-01  8:54   ` Pankaj Gupta
2020-09-24 19:02   ` Dan Williams
2020-09-01  8:33 ` [PATCH v5 3/3] xen: add helpers to allocate unpopulated memory Roger Pau Monne
2020-09-01 14:45   ` Roger Pau Monné
2020-09-01 14:54     ` Jürgen Groß
2020-09-03 15:30   ` Jürgen Groß
2020-09-03 16:38     ` Roger Pau Monné
2020-09-04  7:00       ` Jürgen Groß
2020-09-04  8:42         ` Roger Pau Monné
2020-09-04 12:40           ` Jürgen Groß [this message]
2020-09-04 12:40 ` [PATCH v5 0/3] xen/balloon: fixes for memory hotplug Jürgen Groß

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