On Thu, 07 Jun 2018 22:58:11 +0530 Mahesh J Salgaonkar mahesh@linux.vnet.ibm.com wrote:
From: Mahesh Salgaonkar mahesh@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@vger.kernel.org Suggested-by: Aneesh Kumar K.V aneesh.kumar@linux.vnet.ibm.com Signed-off-by: Mahesh Salgaonkar mahesh@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);
Does this have to be in the RMA region if it's to be accessed with relocation off in the guest?
A comment about it being accessed with relocation off might be helpful too.
Thanks, Nick