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Diffstat (limited to '')
| -rw-r--r-- | Documentation/powerpc/dawr-power9.rst (renamed from Documentation/powerpc/DAWR-POWER9.txt) | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/Documentation/powerpc/DAWR-POWER9.txt b/Documentation/powerpc/dawr-power9.rst index ecdbb076438c..c96ab6befd9c 100644 --- a/Documentation/powerpc/DAWR-POWER9.txt +++ b/Documentation/powerpc/dawr-power9.rst @@ -1,10 +1,11 @@ +===================== DAWR issues on POWER9 -============================ +===================== On POWER9 the Data Address Watchpoint Register (DAWR) can cause a checkstop if it points to cache inhibited (CI) memory. Currently Linux has no way to disinguish CI memory when configuring the DAWR, so (for now) the DAWR is -disabled by this commit: +disabled by this commit:: commit 9654153158d3e0684a1bdb76dbababdb7111d5a0 Author: Michael Neuling <mikey@neuling.org> @@ -12,7 +13,7 @@ disabled by this commit: powerpc: Disable DAWR in the base POWER9 CPU features Technical Details: -============================ +================== DAWR has 6 different ways of being set. 1) ptrace @@ -37,7 +38,7 @@ DAWR on the migration. For xmon, the 'bd' command will return an error on P9. Consequences for users -============================ +====================== For GDB watchpoints (ie 'watch' command) on POWER9 bare metal , GDB will accept the command. Unfortunately since there is no hardware @@ -57,8 +58,8 @@ trapped in GDB. The watchpoint is remembered, so if the guest is migrated back to the POWER8 host, it will start working again. Force enabling the DAWR -============================= -Kernels (since ~v5.2) have an option to force enable the DAWR via: +======================= +Kernels (since ~v5.2) have an option to force enable the DAWR via:: echo Y > /sys/kernel/debug/powerpc/dawr_enable_dangerous @@ -86,5 +87,7 @@ dawr_enable_dangerous file will fail if the hypervisor doesn't support writing the DAWR. To double check the DAWR is working, run this kernel selftest: + tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c + Any errors/failures/skips mean something is wrong. |