When running SMP systems we sometimes were seeing lockups where
IPI interrupts were being raised by never handled.

This looks to be caused by 2 issues in the openrisc interrupt handling
logic.

 1. After clearing an interrupt the openrisc_cpu_set_irq handler will
    always clear PICSR.  This is not correct as masked interrupts
    should still be visible in PICSR.
 2. After setting PICMR (mask register) and exposed interrupts should
    cause an interrupt to be raised.  This was not being done so add it.

This patch fixes both issues.

Signed-off-by: Stafford Horne <shorne@gmail.com>
---
 target/openrisc/cpu.c        | 1 -
 target/openrisc/sys_helper.c | 7 +++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/target/openrisc/cpu.c b/target/openrisc/cpu.c
index 41d1b2a24a..cb9f35f408 100644
--- a/target/openrisc/cpu.c
+++ b/target/openrisc/cpu.c
@@ -98,7 +98,6 @@ static void openrisc_cpu_set_irq(void *opaque, int irq, int level)
         cpu_interrupt(cs, CPU_INTERRUPT_HARD);
     } else {
         cpu_reset_interrupt(cs, CPU_INTERRUPT_HARD);
-        cpu->env.picsr = 0;
     }
 }
 #endif
diff --git a/target/openrisc/sys_helper.c b/target/openrisc/sys_helper.c
index 7c0d3d6187..5336110b5e 100644
--- a/target/openrisc/sys_helper.c
+++ b/target/openrisc/sys_helper.c
@@ -139,6 +139,13 @@ void HELPER(mtspr)(CPUOpenRISCState *env, target_ulong spr, target_ulong rb)
         break;
     case TO_SPR(9, 0):  /* PICMR */
         env->picmr = rb;
+        qemu_mutex_lock_iothread();
+        if (env->picsr & env->picmr) {
+            cpu_interrupt(cs, CPU_INTERRUPT_HARD);
+        } else {
+            cpu_reset_interrupt(cs, CPU_INTERRUPT_HARD);
+        }
+        qemu_mutex_unlock_iothread();
         break;
     case TO_SPR(9, 2):  /* PICSR */
         env->picsr &= ~rb;
-- 
2.36.1

On 7/4/22 02:58, Stafford Horne wrote:
> When running SMP systems we sometimes were seeing lockups where
> IPI interrupts were being raised by never handled.
> 
> This looks to be caused by 2 issues in the openrisc interrupt handling
> logic.
> 
>   1. After clearing an interrupt the openrisc_cpu_set_irq handler will
>      always clear PICSR.  This is not correct as masked interrupts
>      should still be visible in PICSR.
>   2. After setting PICMR (mask register) and exposed interrupts should
>      cause an interrupt to be raised.  This was not being done so add it.
> 
> This patch fixes both issues.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~