| Message ID | 2e3acfe63d289c6fba366e16973c9ab8369e8b75.1631803922.git.christophe.leroy@csgroup.eu (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [v2] powerpc: warn on emulation of dcbz instruction in kernel mode | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_ppctests | success | Successfully ran 8 jobs. |
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 8 jobs. |
| snowpatch_ozlabs/github-powerpc_sparse | success | Successfully ran 4 jobs. |
| snowpatch_ozlabs/github-powerpc_kernel_qemu | success | Successfully ran 24 jobs. |
| snowpatch_ozlabs/github-powerpc_clang | success | Successfully ran 7 jobs. |
On Thu, 16 Sep 2021 16:52:09 +0200, Christophe Leroy wrote: > dcbz instruction shouldn't be used on non-cached memory. Using > it on non-cached memory can result in alignment exception and > implies a heavy handling. > > Instead of silentely emulating the instruction and resulting in high > performance degradation, warn whenever an alignment exception is > taken in kernel mode due to dcbz, so that the user is made aware that > dcbz instruction has been used unexpectedly by the kernel. > > [...] Applied to powerpc/next. [1/1] powerpc: warn on emulation of dcbz instruction in kernel mode https://git.kernel.org/powerpc/c/cbe654c779616807e1e6823c3bdbfe07a10562b8 cheers
diff --git a/arch/powerpc/kernel/align.c b/arch/powerpc/kernel/align.c index bbb4181621dd..bf96b954a4eb 100644 --- a/arch/powerpc/kernel/align.c +++ b/arch/powerpc/kernel/align.c @@ -349,6 +349,7 @@ int fix_alignment(struct pt_regs *regs) if (op.type != CACHEOP + DCBZ) return -EINVAL; PPC_WARN_ALIGNMENT(dcbz, regs); + WARN_ON_ONCE(!user_mode(regs)); r = emulate_dcbz(op.ea, regs); } else { if (type == LARX || type == STCX)
dcbz instruction shouldn't be used on non-cached memory. Using it on non-cached memory can result in alignment exception and implies a heavy handling. Instead of silentely emulating the instruction and resulting in high performance degradation, warn whenever an alignment exception is taken in kernel mode due to dcbz, so that the user is made aware that dcbz instruction has been used unexpectedly by the kernel. Reported-by: Stan Johnson <userm57@yahoo.com> Cc: Finn Thain <fthain@linux-m68k.org> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> --- v2: Warn only when emulating kernel mode --- arch/powerpc/kernel/align.c | 1 + 1 file changed, 1 insertion(+)