[PATCH] parisc: fix a possible DMA corruption

[Mikulas Patocka <mpatocka@redhat.com>]

ARCH_DMA_MINALIGN was defined as 16 - this is too small - it may be 
possible that two unrelated 16-byte allocations share a cache line. If one 
of these allocations is written using DMA and the other is written using 
cached write, the value that was written with DMA may be corrupted.

This commit changes ARCH_DMA_MINALIGN to be 128 - that's the largest 
possible cache line size on parisc.

As different parisc microarchitectures have different cache line size, we 
define arch_slab_minalign(), cache_line_size() and 
dma_get_cache_alignment() so that the kernel may tune slab cache 
parameters dynamically, based on the detected cache line size.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org

---
 arch/parisc/Kconfig             |    1 +
 arch/parisc/include/asm/cache.h |    7 ++++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

Index: linux-6.10/arch/parisc/include/asm/cache.h
===================================================================
--- linux-6.10.orig/arch/parisc/include/asm/cache.h	2023-09-18 11:33:40.000000000 +0200
+++ linux-6.10/arch/parisc/include/asm/cache.h	2024-07-26 20:27:06.000000000 +0200
@@ -20,7 +20,12 @@
 
 #define SMP_CACHE_BYTES L1_CACHE_BYTES
 
-#define ARCH_DMA_MINALIGN	L1_CACHE_BYTES
+#define ARCH_DMA_MINALIGN	128
+#define ARCH_KMALLOC_MINALIGN	8
+
+#define arch_slab_minalign()	((unsigned)dcache_stride)
+#define cache_line_size()	dcache_stride
+#define dma_get_cache_alignment cache_line_size
 
 #define __read_mostly __section(".data..read_mostly")
 
Index: linux-6.10/arch/parisc/Kconfig
===================================================================
--- linux-6.10.orig/arch/parisc/Kconfig	2024-07-23 20:35:34.000000000 +0200
+++ linux-6.10/arch/parisc/Kconfig	2024-07-26 19:41:15.000000000 +0200
@@ -20,6 +20,7 @@ config PARISC
 	select ARCH_SUPPORTS_HUGETLBFS if PA20
 	select ARCH_SUPPORTS_MEMORY_FAILURE
 	select ARCH_STACKWALK
+	select ARCH_HAS_CACHE_LINE_SIZE
 	select ARCH_HAS_DEBUG_VM_PGTABLE
 	select HAVE_RELIABLE_STACKTRACE
 	select DMA_OPS