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 <ravi.bango...@linux.ibm.com> [Fixed build warning reported by kernel test robot] Reported-by: kernel test robot <l...@intel.com> --- v2->v3: - v2: https://lore.kernel.org/r/20201022034039.330365-1-ravi.bango...@linux.ibm.com - Drop first patch which introduced CPU_FTRS_POWER10_DD1. Instead use P1 DD1 PVR direclty in if condition. We can't set CPU_FTRS_POWER10_DD1 inside guest as guest can be migrated to futur version of cpu. 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 | 68 ++++++++++++++++++++++++++++- 1 file changed, 66 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c index 1f4a1efa0074..67297aea5d94 100644 --- a/arch/powerpc/kernel/hw_breakpoint.c +++ b/arch/powerpc/kernel/hw_breakpoint.c @@ -644,6 +644,11 @@ 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. @@ -694,6 +699,58 @@ 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_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_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; @@ -752,8 +809,15 @@ int hw_breakpoint_handler(struct die_args *args) goto reset; if (!nr_hit) { - rc = NOTIFY_DONE; - goto out; + /* Workaround for Power10 DD1 */ + if (mfspr(SPRN_PVR) == 0x800100 && + !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
