Re: [PATCH 2/2] powerpc/watchpoint: Workaround P10 DD1 issue with VSX-32 byte instructions
Hi Ravi,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on powerpc/next]
[also build test WARNING on v5.9 next-20201016]
[cannot apply to mpe/next scottwood/next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url:
https://github.com/0day-ci/linux/commits/Ravi-Bangoria/powerpc-Introduce-POWER10_DD1-feature/20201020-134813
base: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: powerpc-allmodconfig (attached as .config)
compiler: powerpc64-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
wget
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O
~/bin/make.cross
chmod +x ~/bin/make.cross
#
https://github.com/0day-ci/linux/commit/a873a50e35b4c881b6bb53f48ae8ef7bb3e576eb
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review
Ravi-Bangoria/powerpc-Introduce-POWER10_DD1-feature/20201020-134813
git checkout a873a50e35b4c881b6bb53f48ae8ef7bb3e576eb
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross
ARCH=powerpc
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot
All warnings (new ones prefixed by >>):
arch/powerpc/kernel/hw_breakpoint.c: In function
'handle_p10dd1_spurious_exception':
>> arch/powerpc/kernel/hw_breakpoint.c:561:16: warning: variable
>> 'hw_start_addr' set but not used [-Wunused-but-set-variable]
561 | unsigned long hw_start_addr;
|^
vim +/hw_start_addr +561 arch/powerpc/kernel/hw_breakpoint.c
556
557 static void handle_p10dd1_spurious_exception(struct arch_hw_breakpoint
**info,
558 int *hit, unsigned long ea)
559 {
560 int i;
> 561 unsigned long hw_start_addr;
562 unsigned long hw_end_addr;
563
564 /*
565 * Handle spurious exception only when any bp_per_reg is set.
566 * Otherwise this might be created by xmon and not actually a
567 * spurious exception.
568 */
569 for (i = 0; i < nr_wp_slots(); i++) {
570 if (!info[i])
571 continue;
572
573 hw_start_addr = ALIGN_DOWN(info[i]->address,
HW_BREAKPOINT_SIZE);
574 hw_end_addr = ALIGN(info[i]->address + info[i]->len,
HW_BREAKPOINT_SIZE);
575
576 /*
577 * Ending address of DAWR range is less than starting
578 * address of op.
579 */
580 if ((hw_end_addr - 1) >= ea)
581 continue;
582
583 /*
584 * Those addresses need to be in the same or in two
585 * consecutive 512B blocks;
586 */
587 if (((hw_end_addr - 1) >> 10) != (ea >> 10))
588 continue;
589
590 /*
591 * 'op address + 64B' generates an address that has a
592 * carry into bit 52 (crosses 2K boundary).
593 */
594 if ((ea & 0x800) == ((ea + 64) & 0x800))
595 continue;
596
597 break;
598 }
599
600 if (i == nr_wp_slots())
601 return;
602
603 for (i = 0; i < nr_wp_slots(); i++) {
604 if (info[i]) {
605 hit[i] = 1;
606 info[i]->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
607 }
608 }
609 }
610
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-...@lists.01.org
.config.gz
Description: application/gzip
[PATCH 2/2] powerpc/watchpoint: Workaround P10 DD1 issue with VSX-32 byte instructions
POWER10 DD1 has an issue where it generates watchpoint exceptions when it
shouldn't. The conditions where this occur are:
- octword op
- ending address of DAWR range is less than starting address of op
- those addresses need to be in the same or in two consecutive 512B
blocks
- 'op address + 64B' generates an address that has a carry into bit
52 (crosses 2K boundary)
Handle such spurious exception by considering them as extraneous and
emulating/single-steeping instruction without generating an event.
Signed-off-by: Ravi Bangoria
---
Dependency: VSX-32 byte emulation support patches
https://lore.kernel.org/r/20201011050908.72173-1-ravi.bango...@linux.ibm.com
arch/powerpc/kernel/hw_breakpoint.c | 69 -
1 file changed, 67 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/hw_breakpoint.c
b/arch/powerpc/kernel/hw_breakpoint.c
index f4e8f21046f5..4514745d27c3 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -499,6 +499,11 @@ static bool is_larx_stcx_instr(int type)
return type == LARX || type == STCX;
}
+static bool is_octword_vsx_instr(int type, int size)
+{
+ return ((type == LOAD_VSX || type == STORE_VSX) && size == 32);
+}
+
/*
* We've failed in reliably handling the hw-breakpoint. Unregister
* it and throw a warning message to let the user know about it.
@@ -549,6 +554,60 @@ static bool stepping_handler(struct pt_regs *regs, struct
perf_event **bp,
return true;
}
+static void handle_p10dd1_spurious_exception(struct arch_hw_breakpoint **info,
+int *hit, unsigned long ea)
+{
+ int i;
+ unsigned long hw_start_addr;
+ unsigned long hw_end_addr;
+
+ /*
+* Handle spurious exception only when any bp_per_reg is set.
+* Otherwise this might be created by xmon and not actually a
+* spurious exception.
+*/
+ for (i = 0; i < nr_wp_slots(); i++) {
+ if (!info[i])
+ continue;
+
+ hw_start_addr = ALIGN_DOWN(info[i]->address,
HW_BREAKPOINT_SIZE);
+ hw_end_addr = ALIGN(info[i]->address + info[i]->len,
HW_BREAKPOINT_SIZE);
+
+ /*
+* Ending address of DAWR range is less than starting
+* address of op.
+*/
+ if ((hw_end_addr - 1) >= ea)
+ continue;
+
+ /*
+* Those addresses need to be in the same or in two
+* consecutive 512B blocks;
+*/
+ if (((hw_end_addr - 1) >> 10) != (ea >> 10))
+ continue;
+
+ /*
+* 'op address + 64B' generates an address that has a
+* carry into bit 52 (crosses 2K boundary).
+*/
+ if ((ea & 0x800) == ((ea + 64) & 0x800))
+ continue;
+
+ break;
+ }
+
+ if (i == nr_wp_slots())
+ return;
+
+ for (i = 0; i < nr_wp_slots(); i++) {
+ if (info[i]) {
+ hit[i] = 1;
+ info[i]->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
+ }
+ }
+}
+
int hw_breakpoint_handler(struct die_args *args)
{
bool err = false;
@@ -607,8 +666,14 @@ int hw_breakpoint_handler(struct die_args *args)
goto reset;
if (!nr_hit) {
- rc = NOTIFY_DONE;
- goto out;
+ if (cpu_has_feature(CPU_FTR_POWER10_DD1) &&
+ !IS_ENABLED(CONFIG_PPC_8xx) &&
+ is_octword_vsx_instr(type, size)) {
+ handle_p10dd1_spurious_exception(info, hit, ea);
+ } else {
+ rc = NOTIFY_DONE;
+ goto out;
+ }
}
/*
--
2.25.1
