Re: [RFC PATCH v2 02/10] powerpc/book3s: Introduce exclusive emergency stack for machine check exception.
From: Madhavan Srinivasan <hidden>
Date: 2013-08-16 08:59:07
On Friday 16 August 2013 01:34 PM, Mahesh J Salgaonkar wrote:
quoted hunk ↗ jump to hunk
From: Mahesh Salgaonkar <redacted> 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 <redacted> --- 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.
quoted hunk ↗ jump to hunk
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