powerpc/64s: Move HMI IRQ stat from percpu variable to paca.

With the proposed change in percpu bootmem allocator to use page
mapping [1], the percpu first chunk memory area can come from vmalloc
ranges. This makes the HMI (Hypervisor Maintenance Interrupt) handler
crash the kernel whenever percpu variable is accessed in real mode.
This patch fixes this issue by moving the HMI IRQ stat inside paca for
safe access in realmode.

[1] https://lore.kernel.org/linuxppc-dev/20200608070904.387440-1-aneesh.kumar@linux.ibm.com/

Suggested-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/159290806973.3642154.5244613424529764050.stgit@jupiter

diff --git a/arch/powerpc/include/asm/hardirq.h b/arch/powerpc/include/asm/hardirq.h
index f1e9067..f133b59 100644 (file)
--- a/arch/powerpc/include/asm/hardirq.h
+++ b/arch/powerpc/include/asm/hardirq.h
@@ -13,7 +13,6 @@ typedef struct {
        unsigned int pmu_irqs;
        unsigned int mce_exceptions;
        unsigned int spurious_irqs;
-       unsigned int hmi_exceptions;
        unsigned int sreset_irqs;
 #ifdef CONFIG_PPC_WATCHDOG
        unsigned int soft_nmi_irqs;

diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 45a839a..cc07c39 100644 (file)
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -225,6 +225,7 @@ struct paca_struct {
        u16 in_mce;
        u8 hmi_event_available;         /* HMI event is available */
        u8 hmi_p9_special_emu;          /* HMI P9 special emulation */
+       u32 hmi_irqs;                   /* HMI irq stat */
 #endif
        u8 ftrace_enabled;              /* Hard disable ftrace */
 

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 05b1cc0..bf21ebd 100644 (file)
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -621,13 +621,14 @@ 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");
 
+#ifdef CONFIG_PPC_BOOK3S_64
        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, "%10u ", paca_ptrs[j]->hmi_irqs);
                seq_printf(p, "  Hypervisor Maintenance Interrupts\n");
        }
+#endif
 
        seq_printf(p, "%*s: ", prec, "NMI");
        for_each_online_cpu(j)
@@ -665,7 +666,9 @@ 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_BOOK3S_64
+       sum += paca_ptrs[cpu]->hmi_irqs;
+#endif
        sum += per_cpu(irq_stat, cpu).sreset_irqs;
 #ifdef CONFIG_PPC_WATCHDOG
        sum += per_cpu(irq_stat, cpu).soft_nmi_irqs;

diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index c2fa8ee..ada59f6 100644 (file)
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -727,7 +727,7 @@ long hmi_exception_realmode(struct pt_regs *regs)
 {      
        int ret;
 
-       __this_cpu_inc(irq_stat.hmi_exceptions);
+       local_paca->hmi_irqs++;
 
        ret = hmi_handle_debugtrig(regs);
        if (ret >= 0)

diff --git a/arch/powerpc/kvm/book3s_hv_ras.c b/arch/powerpc/kvm/book3s_hv_ras.c
index 79f7d07..6028628 100644 (file)
--- a/arch/powerpc/kvm/book3s_hv_ras.c
+++ b/arch/powerpc/kvm/book3s_hv_ras.c
@@ -244,7 +244,7 @@ long kvmppc_realmode_hmi_handler(void)
 {
        bool resync_req;
 
-       __this_cpu_inc(irq_stat.hmi_exceptions);
+       local_paca->hmi_irqs++;
 
        if (hmi_handle_debugtrig(NULL) >= 0)
                return 1;