| Message ID | 152839248387.25118.579137029955034015.stgit@jupiter.in.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | powerpc/pseries: Machien check handler improvements. | expand |
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
On 06/08/2018 07:01 AM, Nicholas Piggin wrote: > 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? Nope not required. It never gets accessed with relocation off. > > A comment about it being accessed with relocation off might be helpful > too. Sure. Thanks, -Mahesh.
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;