From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 37DBD1A0835 for ; Wed, 4 Jun 2014 18:50:33 +1000 (EST) Received: from e23smtp02.au.ibm.com (e23smtp02.au.ibm.com [202.81.31.144]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id D3CA61400AF for ; Wed, 4 Jun 2014 18:50:32 +1000 (EST) Received: from /spool/local by e23smtp02.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 4 Jun 2014 18:50:31 +1000 Received: from d23relay04.au.ibm.com (d23relay04.au.ibm.com [9.190.234.120]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id DCCBD2BB0040 for ; Wed, 4 Jun 2014 18:50:28 +1000 (EST) Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay04.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s548YVb215925274 for ; Wed, 4 Jun 2014 18:34:32 +1000 Received: from d23av03.au.ibm.com (localhost [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s548oRlN005195 for ; Wed, 4 Jun 2014 18:50:27 +1000 Message-ID: <538EDD61.60801@linux.vnet.ibm.com> Date: Wed, 04 Jun 2014 14:18:33 +0530 From: Anshuman Khandual MIME-Version: 1.0 To: "Aneesh Kumar K.V" Subject: Re: [PATCH] powerpc, xmon: Enable hardware instruction breakpoint support on POWER8 References: <1401451823-25547-1-git-send-email-khandual@linux.vnet.ibm.com> <8761knl6x5.fsf@linux.vnet.ibm.com> <538D654E.8040205@linux.vnet.ibm.com> In-Reply-To: <538D654E.8040205@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Cc: Michael Ellerman , linuxppc-dev@ozlabs.org, mikey@neuling.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 06/03/2014 11:33 AM, Anshuman Khandual wrote: > On 05/30/2014 07:12 PM, Aneesh Kumar K.V wrote: >> > Anshuman Khandual writes: >> > >>> >> This patch enables support for hardware instruction breakpoints on POWER8 with >>> >> the help of a new register called CIABR (Completed Instruction Address Breakpoint >>> >> Register). With this patch, single hardware instruction breakpoint can be added >>> >> and cleared during any active xmon debug session. This hardware based instruction >>> >> breakpoint mechanism works correctly along with the existing TRAP based instruction >>> >> breakpoints available on xmon. Example usage as follows. >>> >> >>> >> (A) Start xmon: >>> >> $echo x > /proc/sysrq-trigger >>> >> SysRq : Entering xmon >>> >> cpu 0x0: Vector: 0 at [c000001f6c67f960] >>> >> pc: c000000000072078: .sysrq_handle_xmon+0x58/0x60 >>> >> lr: c000000000072078: .sysrq_handle_xmon+0x58/0x60 >>> >> sp: c000001f6c67fac0 >>> >> msr: 9000000000009032 >>> >> current = 0xc000001f6e709ac0 >>> >> paca = 0xc00000000fffa000 softe: 0 irq_happened: 0x00 >>> >> pid = 3250, comm = bash >>> >> enter ? for help >>> >> 0:mon> b >>> >> type address >>> >> >>> >> (B) Set the breakpoint: >>> >> 0:mon> ls .power_pmu_add >>> >> .power_pmu_add: c000000000078f50 >>> >> 0:mon> bi c000000000078f50 >>> >> 0:mon> b >>> >> type address >>> >> 1 inst c000000000078f50 .power_pmu_add+0x0/0x2e0 >>> >> 0:mon> ls .perf_event_interrupt >>> >> .perf_event_interrupt: c00000000007aee0 >>> >> 0:mon> bi c00000000007aee0 >>> >> One instruction breakpoint possible with CIABR >>> >> 0:mon> x >>> >> >>> >> (C) Run the workload (with the breakpoint): >>> >> $./perf record ls >>> >> cpu 0x2: Vector: d00 (Single Step) at [c000001f718133a0] >>> >> pc: c000000000078f54: .power_pmu_add+0x4/0x2e0 >>> >> lr: c000000000155be0: .event_sched_in+0x90/0x1d0 >>> >> sp: c000001f71813620 >>> >> msr: 9000000040109032 >>> >> current = 0xc000001f6ce30000 >>> >> paca = 0xc00000000fffa600 softe: 0 irq_happened: 0x01 >>> >> pid = 3270, comm = ls >>> >> std r22,-80(r1) >>> >> enter ? for help >>> >> >>> >> (D) Clear the breakpoint: >>> >> 2:mon> bc >>> >> All breakpoints cleared >>> >> 2:mon> x >>> >> [ perf record: Woken up 1 times to write data ] >>> >> [ perf record: Captured and wrote 0.002 MB perf.data (~66 samples) ] >>> >> >>> >> (E) Run the workload again (without any breakpoints): >>> >> $./perf record ls >>> >> [ perf record: Woken up 1 times to write data ] >>> >> [ perf record: Captured and wrote 0.001 MB perf.data (~61 samples) ] >>> >> >>> >> Signed-off-by: Anshuman Khandual >>> >> --- >>> >> arch/powerpc/xmon/xmon.c | 62 ++++++++++++++++++++++++++++++++++++++++++++---- >>> >> 1 file changed, 58 insertions(+), 4 deletions(-) >>> >> >>> >> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c >>> >> index 3fd1d9a..f74ec83 100644 >>> >> --- a/arch/powerpc/xmon/xmon.c >>> >> +++ b/arch/powerpc/xmon/xmon.c >>> >> @@ -48,6 +48,7 @@ >>> >> #ifdef CONFIG_PPC64 >>> >> #include >>> >> #include >>> >> +#include >>> >> #endif >>> >> >>> >> #include "nonstdio.h" >>> >> @@ -89,6 +90,7 @@ struct bpt { >>> >> /* Bits in bpt.enabled */ >>> >> #define BP_IABR_TE 1 /* IABR translation enabled */ >>> >> #define BP_IABR 2 >>> >> +#define BP_CIABR 4 >>> >> #define BP_TRAP 8 >>> >> #define BP_DABR 0x10 >>> >> >>> >> @@ -97,6 +99,7 @@ static struct bpt bpts[NBPTS]; >>> >> static struct bpt dabr; >>> >> static struct bpt *iabr; >>> >> static unsigned bpinstr = 0x7fe00008; /* trap */ >>> >> +static bool ciabr_used = false; /* CIABR instruction breakpoint */ >>> >> >>> >> #define BP_NUM(bp) ((bp) - bpts + 1) >>> >> >>> >> @@ -269,6 +272,34 @@ static inline void cinval(void *p) >>> >> asm volatile ("dcbi 0,%0; icbi 0,%0" : : "r" (p)); >>> >> } >>> >> >>> >> +static void write_ciabr(unsigned long ciabr) >>> >> +{ >>> >> + if (cpu_has_feature(CPU_FTR_HVMODE)) { >>> >> + mtspr(SPRN_CIABR, ciabr); >>> >> + return; >>> >> + } >>> >> + >>> >> +#ifdef CONFIG_PPC64 >>> >> + plapr_set_ciabr(ciabr); >>> >> +#endif >>> >> +} >>> >> + >>> >> +static void set_ciabr(unsigned long addr) >>> >> +{ >>> >> + addr &= ~CIABR_PRIV; >>> >> + if (cpu_has_feature(CPU_FTR_HVMODE)) >>> >> + addr |= CIABR_PRIV_HYPER; >>> >> + else >>> >> + addr |= CIABR_PRIV_SUPER; >>> >> + write_ciabr(addr); >>> >> +} >>> >> + >>> >> +static void clear_ciabr(void) >>> >> +{ >>> >> + if (cpu_has_feature(CPU_FTR_ARCH_207S)) >>> >> + write_ciabr(0); >>> >> +} >>> >> + >>> >> /* >>> >> * Disable surveillance (the service processor watchdog function) >>> >> * while we are in xmon. >>> >> @@ -764,6 +795,9 @@ static void insert_cpu_bpts(void) >>> >> if (iabr && cpu_has_feature(CPU_FTR_IABR)) >>> >> mtspr(SPRN_IABR, iabr->address >>> >> | (iabr->enabled & (BP_IABR|BP_IABR_TE))); >>> >> + >>> >> + if (iabr && cpu_has_feature(CPU_FTR_ARCH_207S)) >>> >> + set_ciabr(iabr->address); >>> >> } >>> >> >>> >> static void remove_bpts(void) >>> >> @@ -791,6 +825,7 @@ static void remove_cpu_bpts(void) >>> >> hw_breakpoint_disable(); >>> >> if (cpu_has_feature(CPU_FTR_IABR)) >>> >> mtspr(SPRN_IABR, 0); >>> >> + clear_ciabr(); >>> >> } >>> >> >>> >> /* Command interpreting routine */ >>> >> @@ -1124,7 +1159,7 @@ static char *breakpoint_help_string = >>> >> "b [cnt] set breakpoint at given instr addr\n" >>> >> "bc clear all breakpoints\n" >>> >> "bc clear breakpoint number n or at addr\n" >>> >> - "bi [cnt] set hardware instr breakpoint (POWER3/RS64 only)\n" >>> >> + "bi [cnt] set hardware instr breakpoint (POWER3/RS64/POWER8 only)\n" >>> >> "bd [cnt] set hardware data breakpoint\n" >>> >> ""; >>> >> >>> >> @@ -1163,11 +1198,20 @@ bpt_cmds(void) >>> >> break; >>> >> >>> >> case 'i': /* bi - hardware instr breakpoint */ >>> >> - if (!cpu_has_feature(CPU_FTR_IABR)) { >>> >> + if (!cpu_has_feature(CPU_FTR_IABR) && !cpu_has_feature(CPU_FTR_ARCH_207S)) { >>> >> printf("Hardware instruction breakpoint " >>> >> "not supported on this cpu\n"); >>> >> break; >>> >> } >>> >> + >>> >> + if (cpu_has_feature(CPU_FTR_ARCH_207S)) { >>> >> + if (ciabr_used) { >>> >> + printf("One instruction breakpoint " >>> >> + "possible with CIABR\n"); >>> >> + break; >>> >> + } >> > >> > We don't seem to do that with iabr ? Why keep ciabr different > Right now with the IABR implementation if we try to set hardware instruction > breakpoint while one is already there, it just get overridden with the new > address without complaining. I thought with this at least for CIABR cases, > it will complain about it and require the user to clear the breakpoint > explicitly before allowing a new breakpoint. Okay will remove this. > I tried removing the "ciabr_used" variable and all related checks/assignments on it. Then I was able to add all these three address as hardware instruction breakpoint and xmon never complained that it might override the existing actual checkpoint implemented with CIABR. It accepted all the three addresses which can later be listed as below. 0:mon> b type address 1 inst c0000000000830d0 .power_pmu_add+0x0/0x2e0 2 inst c000000000084690 .power_pmu_del+0x0/0x3a0 3 inst c000000000085060 .perf_event_interrupt+0x0/0x480 But in reality, only perf_event_interrupt function's address got written into CIABR register and got triggered with the workload. I dont have a system which has IABR support to test it's behaviour for this situation. But this does not sound okay, we should explicitly inform the user that the hardware instruction breakpoint has been overridden with the latest command or reject the attempt. Looking for some suggestions in this regard. Thank you.