Changeset 36f19c0 in mainline for kernel/arch/sparc64/include/trap/mmu.h

Timestamp:

2007-04-09T16:21:47Z (18 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

ec5b3204

Parents:

183788f1

Message:

Fix a nasty bug in the TLB miss handlers on sparc64.
After we no longer lock the kernel stack in the DTLB,
there is a real danger of nested DTLB misses. The nested
miss can very easily clobber the DTLB Tag Access register.
Therefore, the original miss may not read this register, but
it has to receive its value as an argument. The argument
value is saved in the trap table when it is guaranteed that
the nested TLB miss will not occur.

File:

• kernel/arch/sparc64/include/trap/mmu.h (modified) (2 diffs)

kernel/arch/sparc64/include/trap/mmu.h

@@ -130 +130 @@
 .endif
 
+        /*
+         * Switch from the MM globals.
+         */
         wrpr %g0, PSTATE_PRIV_BIT | PSTATE_AG_BIT, %pstate
+
+        /*
+         * Read the Tag Access register for the higher-level handler.
+         * This is necessary to survive nested DTLB misses.
+         */     
+        mov VA_DMMU_TAG_ACCESS, %g2
+        ldxa [%g2] ASI_DMMU, %g2
+
+        /*
+         * g2 will be passed as an argument to fast_data_access_mmu_miss().
+         */
         PREEMPTIBLE_HANDLER fast_data_access_mmu_miss
 .endm
@@ -143 +157 @@
 .endif
 
+        /*
+         * Switch from the MM globals.
+         */
         wrpr %g0, PSTATE_PRIV_BIT | PSTATE_AG_BIT, %pstate
+
+        /*
+         * Read the Tag Access register for the higher-level handler.
+         * This is necessary to survive nested DTLB misses.
+         */     
+        mov VA_DMMU_TAG_ACCESS, %g2
+        ldxa [%g2] ASI_DMMU, %g2
+
+        /*
+         * g2 will be passed as an argument to fast_data_access_mmu_miss().
+         */
         PREEMPTIBLE_HANDLER fast_data_access_protection
 .endm