[v3 PATCH 1/5] powerpc/pseries: convert rtas_log_buf to linear allocation.

[Mahesh J Salgaonkar]

From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>

rtas_log_buf is a buffer to hold RTAS event data that are communicated
to kernel by hypervisor. This buffer is then used to pass RTAS event
data to user through proc fs. This buffer is allocated from vmalloc
(non-linear mapping) area.

On Machine check interrupt, register r3 points to RTAS extended event
log passed by hypervisor that contains the MCE event. The pseries
machine check handler then logs this error into rtas_log_buf. The
rtas_log_buf is a vmalloc-ed (non-linear) buffer we end up taking up a
page fault (vector 0x300) while accessing it. Since machine check
interrupt handler runs in NMI context we can not afford to take any
page fault. Page faults are not honored in NMI context and causes
kernel panic. This patch fixes this issue by allocating rtas_log_buf
using kmalloc.

Fixes: b96672dd840f ("powerpc: Machine check interrupt is a non-maskable interrupt")
Cc: stable at vger.kernel.org
Suggested-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
---
 arch/powerpc/kernel/rtasd.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/rtasd.c b/arch/powerpc/kernel/rtasd.c
index f915db93cd42..3957d4ae2ba2 100644
--- a/arch/powerpc/kernel/rtasd.c
+++ b/arch/powerpc/kernel/rtasd.c
@@ -559,7 +559,7 @@ static int __init rtas_event_scan_init(void)
 	rtas_error_log_max = rtas_get_error_log_max();
 	rtas_error_log_buffer_max = rtas_error_log_max + sizeof(int);
 
-	rtas_log_buf = vmalloc(rtas_error_log_buffer_max*LOG_NUMBER);
+	rtas_log_buf = kmalloc(rtas_error_log_buffer_max*LOG_NUMBER, GFP_KERNEL);
 	if (!rtas_log_buf) {
 		printk(KERN_ERR "rtasd: no memory\n");
 		return -ENOMEM;