Messages in this thread | | | Subject | Re: [PATCH v5 3/3] xen: add helpers to allocate unpopulated memory | From | Jürgen Groß <> | Date | Fri, 4 Sep 2020 09:00:18 +0200 |
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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.
Juergen
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