[PATCH 4/9] sparc32: flush the cache when a kmap_local mapping is installed

[Magnus Lindholm <linmag7@gmail.com>]

sparc32 defines arch_kmap_local_pre_map() as flush_cache_all(), but
generic highmem has never called that hook. The post-conversion flush
correction moved cache maintenance into this uncalled hook, so a new kmap
can be installed while another mapping of the same page still holds dirty
lines at a different colour.

A writer dirties a MAP_SHARED page through its user mapping on one cpu
while a reader pread()s the same offset on another: on an SS-20 with two
RT626 modules all 100 iterations came back stale, 96288 words wrong. With
the flush restored, 0 of 100.

Flush from arch_kmap_local_post_map(), which generic code does call, on
both the map and the scheduler restore paths. Running after the pte is
installed is safe: the address is not handed to the caller until the hook
returns. Route it and the tlb flush through sparc32_kmap_local_post_map()
and sparc32_kmap_local_tlb_flush() so later patches have somewhere for a
cpu-specific policy.

MBus supplies only optional VA[19:12] "super-set" bits to a virtually
indexed cache, so differing colours remain a synonym problem the bus does
not resolve.

Reference: MBus Interface Specification, SPARC International, 1997, "Basic
Assumptions for Level 2", signal VA[19:12] (MAD[53:46]).

Retain global TLB invalidation. Although the slots are CPU-local, remote
translating cache backends can populate entries for them. Local TLB
maintenance requires those remote translating users to be removed first
and belongs in the later HyperSPARC optimization.

Fixes: f99e02372af2 ("sparc/mm/highmem: flush cache and TLB")
Cc: stable@vger.kernel.org
Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
---
 arch/sparc/include/asm/highmem.h | 14 ++++++++++----
 arch/sparc/mm/srmmu.c            | 21 +++++++++++++++++++++
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/arch/sparc/include/asm/highmem.h b/arch/sparc/include/asm/highmem.h
index b1b915ac604d..14b03f348823 100644
--- a/arch/sparc/include/asm/highmem.h
+++ b/arch/sparc/include/asm/highmem.h
@@ -26,6 +26,10 @@
 #include <asm/vaddrs.h>
 #include <asm/pgtsrmmu.h>
 
+void sparc32_kmap_local_cache_flush(unsigned long vaddr);
+void sparc32_kmap_local_tlb_flush(unsigned long vaddr);
+void sparc32_kmap_local_post_map(unsigned long vaddr, pte_t pteval);
+
 #define kmap_prot __pgprot(SRMMU_ET_PTE | SRMMU_PRIV | SRMMU_CACHE)
 extern pte_t *pkmap_page_table;
 
@@ -48,10 +52,12 @@ extern pte_t *pkmap_page_table;
 #define flush_cache_kmaps()	flush_cache_all()
 
 /* FIXME: Use __flush_*_one(vaddr) instead of flush_*_all() -- Anton */
-#define arch_kmap_local_pre_map(vaddr, pteval)	flush_cache_all()
-#define arch_kmap_local_pre_unmap(vaddr)	flush_cache_all()
-#define arch_kmap_local_post_map(vaddr, pteval)	flush_tlb_all()
-#define arch_kmap_local_post_unmap(vaddr)	flush_tlb_all()
+#define arch_kmap_local_pre_unmap(vaddr) \
+	sparc32_kmap_local_cache_flush(vaddr)
+#define arch_kmap_local_post_map(vaddr, pteval) \
+	sparc32_kmap_local_post_map(vaddr, pteval)
+#define arch_kmap_local_post_unmap(vaddr) \
+	sparc32_kmap_local_tlb_flush(vaddr)
 
 #endif /* __KERNEL__ */
 
diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
index 49d41b33aabf..aa53ec10cd8a 100644
--- a/arch/sparc/mm/srmmu.c
+++ b/arch/sparc/mm/srmmu.c
@@ -88,6 +88,27 @@ static int is_hypersparc;
 
 static int srmmu_cache_pagetables;
 
+void sparc32_kmap_local_cache_flush(unsigned long vaddr)
+{
+	flush_cache_all();
+}
+
+/*
+ * Nothing has touched the new mapping yet, so flushing other aliases of this
+ * page here is as good as doing it before the pte was set.
+ */
+void sparc32_kmap_local_post_map(unsigned long vaddr, pte_t pteval)
+{
+	sparc32_kmap_local_cache_flush(vaddr);
+	sparc32_kmap_local_tlb_flush(vaddr);
+}
+
+void sparc32_kmap_local_tlb_flush(unsigned long vaddr)
+{
+	/* Remote translating cache operations can populate these entries. */
+	flush_tlb_all();
+}
+
 /* these will be initialized in srmmu_nocache_calcsize() */
 static unsigned long srmmu_nocache_size;
 static unsigned long srmmu_nocache_end;
-- 
2.43.0