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linux/arch/parisc
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Mathieu Desnoyers 8690bbcf3b Introduce cpu_dcache_is_aliasing() across all architectures 
Introduce a generic way to query whether the data cache is virtually
aliased on all architectures. Its purpose is to ensure that subsystems
which are incompatible with virtually aliased data caches (e.g. FS_DAX)
can reliably query this.

For data cache aliasing, there are three scenarios dependending on the
architecture. Here is a breakdown based on my understanding:

A) The data cache is always aliasing:

* arc
* csky
* m68k (note: shared memory mappings are incoherent ? SHMLBA is missing there.)
* sh
* parisc

B) The data cache aliasing is statically known or depends on querying CPU
   state at runtime:

* arm (cache_is_vivt() || cache_is_vipt_aliasing())
* mips (cpu_has_dc_aliases)
* nios2 (NIOS2_DCACHE_SIZE > PAGE_SIZE)
* sparc32 (vac_cache_size > PAGE_SIZE)
* sparc64 (L1DCACHE_SIZE > PAGE_SIZE)
* xtensa (DCACHE_WAY_SIZE > PAGE_SIZE)

C) The data cache is never aliasing:

* alpha
* arm64 (aarch64)
* hexagon
* loongarch (but with incoherent write buffers, which are disabled since
             commit d23b7795 ("LoongArch: Change SHMLBA from SZ_64K to PAGE_SIZE"))
* microblaze
* openrisc
* powerpc
* riscv
* s390
* um
* x86

Require architectures in A) and B) to select ARCH_HAS_CPU_CACHE_ALIASING and
implement "cpu_dcache_is_aliasing()".

Architectures in C) don't select ARCH_HAS_CPU_CACHE_ALIASING, and thus
cpu_dcache_is_aliasing() simply evaluates to "false".

Note that this leaves "cpu_icache_is_aliasing()" to be implemented as future
work. This would be useful to gate features like XIP on architectures
which have aliasing CPU dcache-icache but not CPU dcache-dcache.

Use "cpu_dcache" and "cpu_cache" rather than just "dcache" and "cache"
to clarify that we really mean "CPU data cache" and "CPU cache" to
eliminate any possible confusion with VFS "dentry cache" and "page
cache".

Link: https://lore.kernel.org/lkml/20030910210416.GA24258@mail.jlokier.co.uk/
Link: https://lkml.kernel.org/r/20240215144633.96437-9-mathieu.desnoyers@efficios.com
Fixes: d92576f116 ("dax: does not work correctly with virtual aliasing caches")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Michael Sclafani <dm-devel@lists.linux.dev>
Cc: Mike Snitzer <snitzer@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-02-22 15:27:19 -08:00
..
boot parisc: Allow building uncompressed Linux kernel 2023-10-30 14:54:40 +01:00
configs staging: qlge: Retire the driver 2023-10-21 11:52:54 +02:00
include Introduce cpu_dcache_is_aliasing() across all architectures 2024-02-22 15:27:19 -08:00
kernel parisc: BTLB: Fix crash when setting up BTLB at CPU bringup 2024-01-31 13:51:26 +01:00
lib parisc: ucmpdi2: Fix no previous prototype for '__ucmpdi2' warning 2023-08-10 18:34:05 +02:00
math-emu parisc: math-emu: Avoid compiler warnings with W=1 2023-07-03 18:56:03 +02:00
mm parisc: Fix random data corruption from exception handler 2024-01-30 17:18:58 +01:00
net parisc: Add eBPF JIT compiler glue code and Makefile 2023-08-22 10:24:47 +02:00
video arch/parisc: Detect primary video device from device instance 2024-01-12 12:38:37 +01:00
defpalo.conf
install.sh kbuild: factor out the common installation code into scripts/install.sh 2022-05-11 21:45:53 +09:00
Kbuild parisc: Wire up eBPF JIT compiler 2023-08-22 10:24:47 +02:00
Kconfig Introduce cpu_dcache_is_aliasing() across all architectures 2024-02-22 15:27:19 -08:00
Kconfig.debug parisc: Use page table locks only if DEBUG_KERNEL is enabled 2023-08-20 20:23:46 +02:00
Makefile kbuild: use 4-space indentation when followed by conditionals 2024-02-15 06:05:44 +09:00