From 1e9b4507ed98457edb8a892934282b8f63e17246 Mon Sep 17 00:00:00 2001 From: Mahesh Salgaonkar Date: Wed, 30 Oct 2013 20:04:08 +0530 Subject: [PATCH] powerpc/book3s: handle machine check in Linux host. Move machine check entry point into Linux. So far we were dependent on firmware to decode MCE error details and handover the high level info to OS. This patch introduces early machine check routine that saves the MCE information (srr1, srr0, dar and dsisr) to the emergency stack. We allocate stack frame on emergency stack and set the r1 accordingly. This allows us to be prepared to take another exception without loosing context. One thing to note here that, if we get another machine check while ME bit is off then we risk a checkstop. Hence we restrict ourselves to save only MCE information and register saved on PACA_EXMC save are before we turn the ME bit on. We use paca->in_mce flag to differentiate between first entry and nested machine check entry which helps proper use of emergency stack. We increment paca->in_mce every time we enter in early machine check handler and decrement it while leaving. When we enter machine check early handler first time (paca->in_mce == 0), we are sure nobody is using MC emergency stack and allocate a stack frame at the start of the emergency stack. During subsequent entry (paca->in_mce > 0), we know that r1 points inside emergency stack and we allocate separate stack frame accordingly. This prevents us from clobbering MCE information during nested machine checks. The early machine check handler changes are placed under CPU_FTR_HVMODE section. This makes sure that the early machine check handler will get executed only in hypervisor kernel. This is the code flow: Machine Check Interrupt | V 0x200 vector ME=0, IR=0, DR=0 | V +-----------------------------------------------+ |machine_check_pSeries_early: | ME=0, IR=0, DR=0 | Alloc frame on emergency stack | | Save srr1, srr0, dar and dsisr on stack | +-----------------------------------------------+ | (ME=1, IR=0, DR=0, RFID) | V machine_check_handle_early ME=1, IR=0, DR=0 | V +-----------------------------------------------+ | machine_check_early (r3=pt_regs) | ME=1, IR=0, DR=0 | Things to do: (in next patches) | | Flush SLB for SLB errors | | Flush TLB for TLB errors | | Decode and save MCE info | +-----------------------------------------------+ | (Fall through existing exception handler routine.) | V machine_check_pSerie ME=1, IR=0, DR=0 | (ME=1, IR=1, DR=1, RFID) | V machine_check_common ME=1, IR=1, DR=1 . . . Signed-off-by: Mahesh Salgaonkar Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/asm-offsets.c | 4 + arch/powerpc/kernel/exceptions-64s.S | 111 +++++++++++++++++++++++++++ arch/powerpc/kernel/traps.c | 12 +++ 3 files changed, 127 insertions(+) diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 2ea5cc033ec8..41a283956a29 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -232,6 +232,10 @@ int main(void) DEFINE(PACA_DTL_RIDX, offsetof(struct paca_struct, dtl_ridx)); #endif /* CONFIG_PPC_STD_MMU_64 */ DEFINE(PACAEMERGSP, offsetof(struct paca_struct, emergency_sp)); +#ifdef CONFIG_PPC_BOOK3S_64 + DEFINE(PACAMCEMERGSP, offsetof(struct paca_struct, mc_emergency_sp)); + DEFINE(PACA_IN_MCE, offsetof(struct paca_struct, in_mce)); +#endif DEFINE(PACAHWCPUID, offsetof(struct paca_struct, hw_cpu_id)); DEFINE(PACAKEXECSTATE, offsetof(struct paca_struct, kexec_state)); DEFINE(PACA_STARTTIME, offsetof(struct paca_struct, starttime)); diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 9f905e40922e..4034dfb2a530 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -156,7 +156,11 @@ machine_check_pSeries_1: HMT_MEDIUM_PPR_DISCARD SET_SCRATCH0(r13) /* save r13 */ EXCEPTION_PROLOG_0(PACA_EXMC) +BEGIN_FTR_SECTION + b machine_check_pSeries_early +FTR_SECTION_ELSE b machine_check_pSeries_0 +ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE) . = 0x300 .globl data_access_pSeries @@ -405,6 +409,64 @@ denorm_exception_hv: .align 7 /* moved from 0x200 */ +machine_check_pSeries_early: +BEGIN_FTR_SECTION + EXCEPTION_PROLOG_1(PACA_EXMC, NOTEST, 0x200) + /* + * Register contents: + * R13 = PACA + * R9 = CR + * Original R9 to R13 is saved on PACA_EXMC + * + * Switch to mc_emergency stack and handle re-entrancy (though we + * currently don't test for overflow). Save MCE registers srr1, + * srr0, dar and dsisr and then set ME=1 + * + * We use paca->in_mce to check whether this is the first entry or + * nested machine check. We increment paca->in_mce to track nested + * machine checks. + * + * If this is the first entry then set stack pointer to + * paca->mc_emergency_sp, otherwise r1 is already pointing to + * stack frame on mc_emergency stack. + * + * NOTE: We are here with MSR_ME=0 (off), which means we risk a + * checkstop if we get another machine check exception before we do + * rfid with MSR_ME=1. + */ + mr r11,r1 /* Save r1 */ + lhz r10,PACA_IN_MCE(r13) + cmpwi r10,0 /* Are we in nested machine check */ + bne 0f /* Yes, we are. */ + /* First machine check entry */ + ld r1,PACAMCEMERGSP(r13) /* Use MC emergency stack */ +0: subi r1,r1,INT_FRAME_SIZE /* alloc stack frame */ + addi r10,r10,1 /* increment paca->in_mce */ + sth r10,PACA_IN_MCE(r13) + std r11,GPR1(r1) /* Save r1 on the stack. */ + std r11,0(r1) /* make stack chain pointer */ + mfspr r11,SPRN_SRR0 /* Save SRR0 */ + std r11,_NIP(r1) + mfspr r11,SPRN_SRR1 /* Save SRR1 */ + std r11,_MSR(r1) + mfspr r11,SPRN_DAR /* Save DAR */ + std r11,_DAR(r1) + mfspr r11,SPRN_DSISR /* Save DSISR */ + std r11,_DSISR(r1) + std r9,_CCR(r1) /* Save CR in stackframe */ + /* Save r9 through r13 from EXMC save area to stack frame. */ + EXCEPTION_PROLOG_COMMON_2(PACA_EXMC) + mfmsr r11 /* get MSR value */ + ori r11,r11,MSR_ME /* turn on ME bit */ + ori r11,r11,MSR_RI /* turn on RI bit */ + ld r12,PACAKBASE(r13) /* get high part of &label */ + LOAD_HANDLER(r12, machine_check_handle_early) + mtspr SPRN_SRR0,r12 + mtspr SPRN_SRR1,r11 + rfid + b . /* prevent speculative execution */ +END_FTR_SECTION_IFSET(CPU_FTR_HVMODE) + machine_check_pSeries: .globl machine_check_fwnmi machine_check_fwnmi: @@ -712,6 +774,55 @@ machine_check_common: bl .machine_check_exception b .ret_from_except +#define MACHINE_CHECK_HANDLER_WINDUP \ + /* Clear MSR_RI before setting SRR0 and SRR1. */\ + li r0,MSR_RI; \ + mfmsr r9; /* get MSR value */ \ + andc r9,r9,r0; \ + mtmsrd r9,1; /* Clear MSR_RI */ \ + /* Move original SRR0 and SRR1 into the respective regs */ \ + ld r9,_MSR(r1); \ + mtspr SPRN_SRR1,r9; \ + ld r3,_NIP(r1); \ + mtspr SPRN_SRR0,r3; \ + ld r9,_CTR(r1); \ + mtctr r9; \ + ld r9,_XER(r1); \ + mtxer r9; \ + ld r9,_LINK(r1); \ + mtlr r9; \ + REST_GPR(0, r1); \ + REST_8GPRS(2, r1); \ + REST_GPR(10, r1); \ + ld r11,_CCR(r1); \ + mtcr r11; \ + /* Decrement paca->in_mce. */ \ + lhz r12,PACA_IN_MCE(r13); \ + subi r12,r12,1; \ + sth r12,PACA_IN_MCE(r13); \ + REST_GPR(11, r1); \ + REST_2GPRS(12, r1); \ + /* restore original r1. */ \ + ld r1,GPR1(r1) + + /* + * Handle machine check early in real mode. We come here with + * ME=1, MMU (IR=0 and DR=0) off and using MC emergency stack. + */ + .align 7 + .globl machine_check_handle_early +machine_check_handle_early: +BEGIN_FTR_SECTION + std r0,GPR0(r1) /* Save r0 */ + EXCEPTION_PROLOG_COMMON_3(0x200) + bl .save_nvgprs + addi r3,r1,STACK_FRAME_OVERHEAD + bl .machine_check_early + /* Deliver the machine check to host kernel in V mode. */ + MACHINE_CHECK_HANDLER_WINDUP + b machine_check_pSeries +END_FTR_SECTION_IFSET(CPU_FTR_HVMODE) + STD_EXCEPTION_COMMON_ASYNC(0x500, hardware_interrupt, do_IRQ) STD_EXCEPTION_COMMON_ASYNC(0x900, decrementer, .timer_interrupt) STD_EXCEPTION_COMMON(0x980, hdecrementer, .hdec_interrupt) diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index 907a472f9a9e..97a1ce72e130 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -285,6 +285,18 @@ void system_reset_exception(struct pt_regs *regs) /* What should we do here? We could issue a shutdown or hard reset. */ } + +/* + * This function is called in real mode. Strictly no printk's please. + * + * regs->nip and regs->msr contains srr0 and ssr1. + */ +long machine_check_early(struct pt_regs *regs) +{ + /* TODO: handle/decode machine check reason */ + return 0; +} + #endif /* -- 2.30.2