| Message ID | 20130816080410.680.46919.stgit@mars.in.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Friday 16 August 2013 01:34 PM, Mahesh J Salgaonkar wrote: > From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com> > > This patch introduces exclusive emergency stack for machine check exception. > We use emergency stack to handle machine check exception so that we can save > MCE information (srr1, srr0, dar and dsisr) before turning on ME bit and be > ready for re-entrancy. This helps us to prevent clobbering of MCE information > in case of nested machine checks. > > The reason for using emergency stack over normal kernel stack is that the > machine check might occur in the middle of setting up a stack frame which may > result into improper use of kernel stack. > > Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com> > --- > arch/powerpc/include/asm/paca.h | 9 +++++++++ > arch/powerpc/kernel/setup_64.c | 8 +++++++- > arch/powerpc/xmon/xmon.c | 2 ++ > 3 files changed, 18 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h > index 77c91e7..b4ca4e9 100644 > --- a/arch/powerpc/include/asm/paca.h > +++ b/arch/powerpc/include/asm/paca.h > @@ -147,6 +147,15 @@ struct paca_struct { > */ > struct opal_machine_check_event *opal_mc_evt; > #endif > +#ifdef CONFIG_PPC_BOOK3S_64 > + /* Exclusive emergency stack pointer for machine check exception. */ > + void *mc_emergency_sp; > + /* > + * Flag to check whether we are in machine check early handler > + * and already using emergency stack. > + */ > + u16 in_mce; > +#endif > > /* Stuff for accurate time accounting */ > u64 user_time; /* accumulated usermode TB ticks */ > diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c > index 389fb807..3fdbdb0 100644 > --- a/arch/powerpc/kernel/setup_64.c > +++ b/arch/powerpc/kernel/setup_64.c > @@ -529,7 +529,8 @@ static void __init exc_lvl_early_init(void) > > /* > * Stack space used when we detect a bad kernel stack pointer, and > - * early in SMP boots before relocation is enabled. > + * early in SMP boots before relocation is enabled. Exclusive emergency > + * stack for machine checks. > */ > static void __init emergency_stack_init(void) > { > @@ -552,6 +553,11 @@ static void __init emergency_stack_init(void) > sp = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit); > sp += THREAD_SIZE; > paca[i].emergency_sp = __va(sp); > + > + /* emergency stack for machine check exception handling. */ > + sp = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit); > + sp += THREAD_SIZE; > + paca[i].mc_emergency_sp = __va(sp); > } > } > Just a concern, kindly ignore it if it is irrelevant. you have defined mc_emergency_sp under CONFIG_PPC_BOOK3S_64, but assigning memory in a common code. This may break build for other configs such as like ppc64e_defconfig. > diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c > index 96bf5bd..147a5e98 100644 > --- a/arch/powerpc/xmon/xmon.c > +++ b/arch/powerpc/xmon/xmon.c > @@ -2044,6 +2044,8 @@ static void dump_one_paca(int cpu) > DUMP(p, stab_addr, "lx"); > #endif > DUMP(p, emergency_sp, "p"); > + DUMP(p, mc_emergency_sp, "p"); > + DUMP(p, in_mce, "x"); > DUMP(p, data_offset, "lx"); > DUMP(p, hw_cpu_id, "x"); > DUMP(p, cpu_start, "x"); > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev >
On 08/16/2013 02:29 PM, Madhavan Srinivasan wrote: > On Friday 16 August 2013 01:34 PM, Mahesh J Salgaonkar wrote: >> From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com> >> >> This patch introduces exclusive emergency stack for machine check exception. >> We use emergency stack to handle machine check exception so that we can save >> MCE information (srr1, srr0, dar and dsisr) before turning on ME bit and be >> ready for re-entrancy. This helps us to prevent clobbering of MCE information >> in case of nested machine checks. >> >> The reason for using emergency stack over normal kernel stack is that the >> machine check might occur in the middle of setting up a stack frame which may >> result into improper use of kernel stack. >> >> Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com> >> --- >> arch/powerpc/include/asm/paca.h | 9 +++++++++ >> arch/powerpc/kernel/setup_64.c | 8 +++++++- >> arch/powerpc/xmon/xmon.c | 2 ++ >> 3 files changed, 18 insertions(+), 1 deletion(-) >> >> diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h >> index 77c91e7..b4ca4e9 100644 >> --- a/arch/powerpc/include/asm/paca.h >> +++ b/arch/powerpc/include/asm/paca.h >> @@ -147,6 +147,15 @@ struct paca_struct { >> */ >> struct opal_machine_check_event *opal_mc_evt; >> #endif >> +#ifdef CONFIG_PPC_BOOK3S_64 >> + /* Exclusive emergency stack pointer for machine check exception. */ >> + void *mc_emergency_sp; >> + /* >> + * Flag to check whether we are in machine check early handler >> + * and already using emergency stack. >> + */ >> + u16 in_mce; >> +#endif >> >> /* Stuff for accurate time accounting */ >> u64 user_time; /* accumulated usermode TB ticks */ >> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c >> index 389fb807..3fdbdb0 100644 >> --- a/arch/powerpc/kernel/setup_64.c >> +++ b/arch/powerpc/kernel/setup_64.c >> @@ -529,7 +529,8 @@ static void __init exc_lvl_early_init(void) >> >> /* >> * Stack space used when we detect a bad kernel stack pointer, and >> - * early in SMP boots before relocation is enabled. >> + * early in SMP boots before relocation is enabled. Exclusive emergency >> + * stack for machine checks. >> */ >> static void __init emergency_stack_init(void) >> { >> @@ -552,6 +553,11 @@ static void __init emergency_stack_init(void) >> sp = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit); >> sp += THREAD_SIZE; >> paca[i].emergency_sp = __va(sp); >> + >> + /* emergency stack for machine check exception handling. */ >> + sp = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit); >> + sp += THREAD_SIZE; >> + paca[i].mc_emergency_sp = __va(sp); >> } >> } >> > Just a concern, kindly ignore it if it is irrelevant. > you have defined mc_emergency_sp under CONFIG_PPC_BOOK3S_64, but > assigning memory in a common code. This may break build for other > configs such as like ppc64e_defconfig. Nice catch. Will fix it in next spin. Thanks, -Mahesh.
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h index 77c91e7..b4ca4e9 100644 --- a/arch/powerpc/include/asm/paca.h +++ b/arch/powerpc/include/asm/paca.h @@ -147,6 +147,15 @@ struct paca_struct { */ struct opal_machine_check_event *opal_mc_evt; #endif +#ifdef CONFIG_PPC_BOOK3S_64 + /* Exclusive emergency stack pointer for machine check exception. */ + void *mc_emergency_sp; + /* + * Flag to check whether we are in machine check early handler + * and already using emergency stack. + */ + u16 in_mce; +#endif /* Stuff for accurate time accounting */ u64 user_time; /* accumulated usermode TB ticks */ diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index 389fb807..3fdbdb0 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -529,7 +529,8 @@ static void __init exc_lvl_early_init(void) /* * Stack space used when we detect a bad kernel stack pointer, and - * early in SMP boots before relocation is enabled. + * early in SMP boots before relocation is enabled. Exclusive emergency + * stack for machine checks. */ static void __init emergency_stack_init(void) { @@ -552,6 +553,11 @@ static void __init emergency_stack_init(void) sp = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit); sp += THREAD_SIZE; paca[i].emergency_sp = __va(sp); + + /* emergency stack for machine check exception handling. */ + sp = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit); + sp += THREAD_SIZE; + paca[i].mc_emergency_sp = __va(sp); } } diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index 96bf5bd..147a5e98 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -2044,6 +2044,8 @@ static void dump_one_paca(int cpu) DUMP(p, stab_addr, "lx"); #endif DUMP(p, emergency_sp, "p"); + DUMP(p, mc_emergency_sp, "p"); + DUMP(p, in_mce, "x"); DUMP(p, data_offset, "lx"); DUMP(p, hw_cpu_id, "x"); DUMP(p, cpu_start, "x");