[PATCH v4 10/16] powerpc/pseries: machine check use rtas_call_unlocked with args on stack
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2020-05-08 04:57:37
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
With the previous patch, machine checks can use rtas_call_unlocked which avoids the rtas spinlock which would deadlock if a machine check hits while making an rtas call. This also avoids the complex rtas error logging which has more rtas calls and includes kmalloc (which can return memory beyond RMA, which would also crash). Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/platforms/pseries/ras.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index b2adba59f0ff..ce1665e58d9b 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c@@ -468,7 +468,15 @@ static struct rtas_error_log *fwnmi_get_errinfo(struct pt_regs *regs) */ static void fwnmi_release_errinfo(void) { - int ret = rtas_call(ibm_nmi_interlock_token, 0, 1, NULL); + struct rtas_args rtas_args; + int ret; + + /* + * On pseries, the machine check stack is limited to under 4GB, so + * args can be on-stack. + */ + rtas_call_unlocked(&rtas_args, ibm_nmi_interlock_token, 0, 1, NULL); + ret = be32_to_cpu(rtas_args.rets[0]); if (ret != 0) printk(KERN_ERR "FWNMI: nmi-interlock failed: %d\n", ret); }
--
2.23.0