powerpc/book3s: Add basic infrastructure to handle HMI in Linux.

Handle Hypervisor Maintenance Interrupt (HMI) in Linux. This patch implements
basic infrastructure to handle HMI in Linux host. The design is to invoke
opal handle hmi in real mode for recovery and set irq_pending when we hit HMI.
During check_irq_replay pull opal hmi event and print hmi info on console.

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

13 files changed, 139 insertions, 3 deletions

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 13a63379e496..77f52b26dad6 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -425,6 +425,8 @@ label##_relon_hv:						\
 #define SOFTEN_VALUE_0xa00      PACA_IRQ_DBELL
 #define SOFTEN_VALUE_0xe80      PACA_IRQ_DBELL
 #define SOFTEN_VALUE_0xe82      PACA_IRQ_DBELL
+#define SOFTEN_VALUE_0xe60      PACA_IRQ_HMI
+#define SOFTEN_VALUE_0xe62      PACA_IRQ_HMI
 
 #define __SOFTEN_TEST(h, vec)                                           \
         lbz     r10,PACASOFTIRQEN(r13);                                 \
diff --git a/arch/powerpc/include/asm/hardirq.h b/arch/powerpc/include/asm/hardirq.h
index 418fb654370d..1bbb3013d6aa 100644
--- a/arch/powerpc/include/asm/hardirq.h
+++ b/arch/powerpc/include/asm/hardirq.h
@@ -11,6 +11,7 @@ typedef struct {
         unsigned int pmu_irqs;
         unsigned int mce_exceptions;
         unsigned int spurious_irqs;
+        unsigned int hmi_exceptions;
 #ifdef CONFIG_PPC_DOORBELL
         unsigned int doorbell_irqs;
 #endif
diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
index 10be1dd01c6b..b59ac27a6b7d 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -25,6 +25,7 @@
 #define PACA_IRQ_EE             0x04
 #define PACA_IRQ_DEC            0x08 /* Or FIT */
 #define PACA_IRQ_EE_EDGE        0x10 /* BookE only */
+#define PACA_IRQ_HMI            0x20
 
 #endif /* CONFIG_PPC64 */
 
diff --git a/arch/powerpc/include/asm/kvm_asm.h b/arch/powerpc/include/asm/kvm_asm.h
index 9601741080e5..ecf7e133a4f2 100644
--- a/arch/powerpc/include/asm/kvm_asm.h
+++ b/arch/powerpc/include/asm/kvm_asm.h
@@ -98,6 +98,7 @@
 #define BOOK3S_INTERRUPT_H_DATA_STORAGE 0xe00
 #define BOOK3S_INTERRUPT_H_INST_STORAGE 0xe20
 #define BOOK3S_INTERRUPT_H_EMUL_ASSIST  0xe40
+#define BOOK3S_INTERRUPT_HMI            0xe60
 #define BOOK3S_INTERRUPT_H_DOORBELL     0xe80
 #define BOOK3S_INTERRUPT_PERFMON        0xf00
 #define BOOK3S_INTERRUPT_ALTIVEC        0xf20
diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h
index 5c7e74ddee4c..44e90516519b 100644
--- a/arch/powerpc/include/asm/machdep.h
+++ b/arch/powerpc/include/asm/machdep.h
@@ -174,6 +174,10 @@ struct machdep_calls {
         /* Exception handlers */
         int             (*system_reset_exception)(struct pt_regs *regs);
         int             (*machine_check_exception)(struct pt_regs *regs);
+        int             (*handle_hmi_exception)(struct pt_regs *regs);
+
+        /* Early exception handlers called in realmode */
+        int             (*hmi_exception_early)(struct pt_regs *regs);
 
         /* Called during machine check exception to retrive fixup address. */
         bool            (*mce_check_early_recovery)(struct pt_regs *regs);
diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 7f5fd5396261..efc16c37b959 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -915,6 +915,8 @@ extern void opal_msglog_init(void);
 
 extern int opal_machine_check(struct pt_regs *regs);
 extern bool opal_mce_check_early_recovery(struct pt_regs *regs);
+extern int opal_hmi_exception_early(struct pt_regs *regs);
+extern int opal_handle_hmi_exception(struct pt_regs *regs);
 
 extern void opal_shutdown(void);
 extern int opal_resync_timebase(void);
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index d6b22e8c8ee1..5bbd1bc8c3b0 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -915,6 +915,11 @@ restore_check_irq_replay:
         addi    r3,r1,STACK_FRAME_OVERHEAD;
         bl      do_IRQ
         b       ret_from_except
+1:      cmpwi   cr0,r3,0xe60
+        bne     1f
+        addi    r3,r1,STACK_FRAME_OVERHEAD;
+        bl      handle_hmi_exception
+        b       ret_from_except
 1:      cmpwi   cr0,r3,0x900
         bne     1f
         addi    r3,r1,STACK_FRAME_OVERHEAD;
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index f521b2dac051..6144d5a6bfe7 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -335,7 +335,7 @@ emulation_assist_trampoline:
 hv_exception_trampoline:
         SET_SCRATCH0(r13)
         EXCEPTION_PROLOG_0(PACA_EXGEN)
-        b       hmi_exception_hv
+        b       hmi_exception_early
 
         . = 0xe80
 hv_doorbell_trampoline:
@@ -589,8 +589,64 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
         KVM_HANDLER(PACA_EXGEN, EXC_HV, 0xe22)
         STD_EXCEPTION_HV_OOL(0xe42, emulation_assist)
         KVM_HANDLER(PACA_EXGEN, EXC_HV, 0xe42)
-        STD_EXCEPTION_HV_OOL(0xe62, hmi_exception) /* need to flush cache ? */
+        MASKABLE_EXCEPTION_HV_OOL(0xe62, hmi_exception)
         KVM_HANDLER(PACA_EXGEN, EXC_HV, 0xe62)
+
+        .globl hmi_exception_early
+hmi_exception_early:
+        EXCEPTION_PROLOG_1(PACA_EXGEN, NOTEST, 0xe60)
+        mr      r10,r1                  /* Save r1                      */
+        ld      r1,PACAEMERGSP(r13)     /* Use emergency stack          */
+        subi    r1,r1,INT_FRAME_SIZE    /* alloc stack frame            */
+        std     r9,_CCR(r1)             /* save CR in stackframe        */
+        mfspr   r11,SPRN_HSRR0          /* Save HSRR0 */
+        std     r11,_NIP(r1)            /* save HSRR0 in stackframe     */
+        mfspr   r12,SPRN_HSRR1          /* Save SRR1 */
+        std     r12,_MSR(r1)            /* save SRR1 in stackframe      */
+        std     r10,0(r1)               /* make stack chain pointer     */
+        std     r0,GPR0(r1)             /* save r0 in stackframe        */
+        std     r10,GPR1(r1)            /* save r1 in stackframe        */
+        EXCEPTION_PROLOG_COMMON_2(PACA_EXGEN)
+        EXCEPTION_PROLOG_COMMON_3(0xe60)
+        addi    r3,r1,STACK_FRAME_OVERHEAD
+        bl      hmi_exception_realmode
+        /* Windup the stack. */
+        /* 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 HSRR0 and HSRR1 into the respective regs */
+        ld      r9,_MSR(r1)
+        mtspr   SPRN_HSRR1,r9
+        ld      r3,_NIP(r1)
+        mtspr   SPRN_HSRR0,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
+        REST_GPR(11, r1)
+        REST_2GPRS(12, r1)
+        /* restore original r1. */
+        ld      r1,GPR1(r1)
+
+        /*
+         * Go to virtual mode and pull the HMI event information from
+         * firmware.
+         */
+        .globl hmi_exception_after_realmode
+hmi_exception_after_realmode:
+        SET_SCRATCH0(r13)
+        EXCEPTION_PROLOG_0(PACA_EXGEN)
+        b       hmi_exception_hv
+
         MASKABLE_EXCEPTION_HV_OOL(0xe82, h_doorbell)
         KVM_HANDLER(PACA_EXGEN, EXC_HV, 0xe82)
 
@@ -611,6 +667,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
  * - If it was a decrementer interrupt, we bump the dec to max and and return.
  * - If it was a doorbell we return immediately since doorbells are edge
  *   triggered and won't automatically refire.
+ * - If it was a HMI we return immediately since we handled it in realmode
+ *   and it won't refire.
  * - else we hard disable and return.
  * This is called with r10 containing the value to OR to the paca field.
  */
@@ -628,6 +686,8 @@ masked_##_H##interrupt:					\
         b       2f;                                     \
 1:      cmpwi   r10,PACA_IRQ_DBELL;                     \
         beq     2f;                                     \
+        cmpwi   r10,PACA_IRQ_HMI;                       \
+        beq     2f;                                     \
         mfspr   r10,SPRN_##_H##SRR1;                    \
         rldicl  r10,r10,48,1; /* clear MSR_EE */        \
         rotldi  r10,r10,16;                             \
@@ -767,7 +827,7 @@ kvmppc_skip_Hinterrupt:
         STD_EXCEPTION_COMMON(0xd00, single_step, single_step_exception)
         STD_EXCEPTION_COMMON(0xe00, trap_0e, unknown_exception)
         STD_EXCEPTION_COMMON(0xe40, emulation_assist, emulation_assist_interrupt)
-        STD_EXCEPTION_COMMON(0xe60, hmi_exception, unknown_exception)
+        STD_EXCEPTION_COMMON_ASYNC(0xe60, hmi_exception, handle_hmi_exception)
 #ifdef CONFIG_PPC_DOORBELL
         STD_EXCEPTION_COMMON_ASYNC(0xe80, h_doorbell, doorbell_exception)
 #else
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 248ee7e5bebd..4c5891de162e 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -189,6 +189,11 @@ notrace unsigned int __check_irq_replay(void)
         }
 #endif /* CONFIG_PPC_BOOK3E */
 
+        /* Check if an hypervisor Maintenance interrupt happened */
+        local_paca->irq_happened &= ~PACA_IRQ_HMI;
+        if (happened & PACA_IRQ_HMI)
+                return 0xe60;
+
         /* There should be nothing left ! */
         BUG_ON(local_paca->irq_happened != 0);
 
@@ -377,6 +382,14 @@ int arch_show_interrupts(struct seq_file *p, int prec)
                 seq_printf(p, "%10u ", per_cpu(irq_stat, j).mce_exceptions);
         seq_printf(p, "  Machine check exceptions\n");
 
+        if (cpu_has_feature(CPU_FTR_HVMODE)) {
+                seq_printf(p, "%*s: ", prec, "HMI");
+                for_each_online_cpu(j)
+                        seq_printf(p, "%10u ",
+                                        per_cpu(irq_stat, j).hmi_exceptions);
+                seq_printf(p, "  Hypervisor Maintenance Interrupts\n");
+        }
+
 #ifdef CONFIG_PPC_DOORBELL
         if (cpu_has_feature(CPU_FTR_DBELL)) {
                 seq_printf(p, "%*s: ", prec, "DBL");
@@ -400,6 +413,7 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
         sum += per_cpu(irq_stat, cpu).mce_exceptions;
         sum += per_cpu(irq_stat, cpu).spurious_irqs;
         sum += per_cpu(irq_stat, cpu).timer_irqs_others;
+        sum += per_cpu(irq_stat, cpu).hmi_exceptions;
 #ifdef CONFIG_PPC_DOORBELL
         sum += per_cpu(irq_stat, cpu).doorbell_irqs;
 #endif
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index cb9cfe448ee8..0dc43f9932cf 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -302,6 +302,16 @@ long machine_check_early(struct pt_regs *regs)
         return handled;
 }
 
+long hmi_exception_realmode(struct pt_regs *regs)
+{
+        __get_cpu_var(irq_stat).hmi_exceptions++;
+
+        if (ppc_md.hmi_exception_early)
+                ppc_md.hmi_exception_early(regs);
+
+        return 0;
+}
+
 #endif
 
 /*
@@ -738,6 +748,20 @@ void SMIException(struct pt_regs *regs)
         die("System Management Interrupt", regs, SIGABRT);
 }
 
+void handle_hmi_exception(struct pt_regs *regs)
+{
+        struct pt_regs *old_regs;
+
+        old_regs = set_irq_regs(regs);
+        irq_enter();
+
+        if (ppc_md.handle_hmi_exception)
+                ppc_md.handle_hmi_exception(regs);
+
+        irq_exit();
+        set_irq_regs(old_regs);
+}
+
 void unknown_exception(struct pt_regs *regs)
 {
         enum ctx_state prev_state = exception_enter();
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 868347ef09fd..0de9309b9a55 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -159,6 +159,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
         cmpwi   r12, BOOK3S_INTERRUPT_EXTERNAL
 BEGIN_FTR_SECTION
         beq     11f
+        cmpwi   cr2, r12, BOOK3S_INTERRUPT_HMI
+        beq     cr2, 14f                        /* HMI check */
 END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
 
         /* RFI into the highmem handler, or branch to interrupt handler */
@@ -179,6 +181,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
 
 13:     b       machine_check_fwnmi
 
+14:     mtspr   SPRN_HSRR0, r8
+        mtspr   SPRN_HSRR1, r7
+        b       hmi_exception_after_realmode
+
 kvmppc_primary_no_guest:
         /* We handle this much like a ceded vcpu */
         /* set our bit in napping_threads */
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 6ef2e5c5bc64..d20d69921376 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -514,6 +514,20 @@ int opal_machine_check(struct pt_regs *regs)
         return 0;
 }
 
+/* Early hmi handler called in real mode. */
+int opal_hmi_exception_early(struct pt_regs *regs)
+{
+        /* TODO: Call opal hmi handler. */
+        return 0;
+}
+
+/* HMI exception handler called in virtual mode during check_irq_replay. */
+int opal_handle_hmi_exception(struct pt_regs *regs)
+{
+        /* TODO: Retrive and print HMI event from OPAL. */
+        return 0;
+}
+
 static uint64_t find_recovery_address(uint64_t nip)
 {
         int i;
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index d9b88fa7c5a3..5a0e2dc6de5f 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -264,6 +264,8 @@ static void __init pnv_setup_machdep_opal(void)
         ppc_md.halt = pnv_halt;
         ppc_md.machine_check_exception = opal_machine_check;
         ppc_md.mce_check_early_recovery = opal_mce_check_early_recovery;
+        ppc_md.hmi_exception_early = opal_hmi_exception_early;
+        ppc_md.handle_hmi_exception = opal_handle_hmi_exception;
 }
 
 #ifdef CONFIG_PPC_POWERNV_RTAS