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authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>2024-02-15 17:46:32 +0300
committerAndrew Morton <akpm@linux-foundation.org>2024-02-23 02:27:19 +0300
commit8690bbcf3b7010b31fdbf3851e1add6ae19b8624 (patch)
tree8b571309484074613ae93ac95b9d75d6b8144e4b /arch/m68k
parent1df4ca0155acb37b9b1d03ab91323d70a309ff54 (diff)
downloadlinux-8690bbcf3b7010b31fdbf3851e1add6ae19b8624.tar.xz
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: d92576f1167c ("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>
Diffstat (limited to 'arch/m68k')
-rw-r--r--arch/m68k/Kconfig1
-rw-r--r--arch/m68k/include/asm/cachetype.h9
2 files changed, 10 insertions, 0 deletions
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index 4b3e93cac723..a9c3e3de0c6d 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -3,6 +3,7 @@ config M68K
bool
default y
select ARCH_32BIT_OFF_T
+ select ARCH_HAS_CPU_CACHE_ALIASING
select ARCH_HAS_BINFMT_FLAT
select ARCH_HAS_CPU_FINALIZE_INIT if MMU
select ARCH_HAS_CURRENT_STACK_POINTER
diff --git a/arch/m68k/include/asm/cachetype.h b/arch/m68k/include/asm/cachetype.h
new file mode 100644
index 000000000000..7fad5d9ab8fe
--- /dev/null
+++ b/arch/m68k/include/asm/cachetype.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_M68K_CACHETYPE_H
+#define __ASM_M68K_CACHETYPE_H
+
+#include <linux/types.h>
+
+#define cpu_dcache_is_aliasing() true
+
+#endif