Messages in this thread | | | Subject | Re: [PATCH v5 3/3] xen: add helpers to allocate unpopulated memory | From | Jürgen Groß <> | Date | Thu, 3 Sep 2020 17:30:07 +0200 |
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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
Juergen
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