[PATCH kernel v4 0/2] powerpc/xive: Drop deregistered irqs

[PATCH kernel v4 0/2] powerpc/xive: Drop deregistered irqs

[Alexey Kardashevskiy]

Now 2 patches.
v3 is here: https://patchwork.ozlabs.org/patch/1133106/


This is based on sha1
a2b6f26c264e Christophe Leroy "powerpc/module64: Use symbolic instructions names.".

Please comment. Thanks.



Alexey Kardashevskiy (2):
  powerpc: Add handler for orphaned interrupts
  powerpc/xive: Drop current cpu priority for orphaned interrupts

 arch/powerpc/include/asm/machdep.h |  3 +++
 arch/powerpc/kernel/irq.c          |  9 ++++++---
 arch/powerpc/sysdev/xive/common.c  | 18 ++++++++++++++++++
 3 files changed, 27 insertions(+), 3 deletions(-)

-- 
2.17.1

[PATCH kernel v4 1/2] powerpc: Add handler for orphaned interrupts

[Alexey Kardashevskiy]

The test on generic_handle_irq() catches interrupt events that
were served on a target CPU while the source interrupt was being
shutdown on another CPU. This may lead to a blocked interrupt queue
on a target CPU so if there is another assigned irq on that CPU, that
device stops working.

This adds necessary infrastructure to allow platform to deal with it.
The next patch implements it for XIVE.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 arch/powerpc/include/asm/machdep.h | 3 +++
 arch/powerpc/kernel/irq.c          | 9 ++++++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h
index c43d6eca9edd..6cc14e28e89a 100644
--- a/arch/powerpc/include/asm/machdep.h
+++ b/arch/powerpc/include/asm/machdep.h
@@ -59,6 +59,9 @@ struct machdep_calls {
 	/* Return an irq, or 0 to indicate there are none pending. */
 	unsigned int	(*get_irq)(void);
 
+	/* Drops irq if it does not have a valid descriptor */
+	void		(*orphan_irq)(unsigned int irq);
+
 	/* PCI stuff */
 	/* Called after allocating resources */
 	void		(*pcibios_fixup)(void);
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 5645bc9cbc09..e0689dcb17f0 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -632,10 +632,13 @@ void __do_irq(struct pt_regs *regs)
 	may_hard_irq_enable();
 
 	/* And finally process it */
-	if (unlikely(!irq))
+	if (unlikely(!irq)) {
 		__this_cpu_inc(irq_stat.spurious_irqs);
-	else
-		generic_handle_irq(irq);
+	} else if (generic_handle_irq(irq)) {
+		if (ppc_md.orphan_irq)
+			ppc_md.orphan_irq(irq);
+		__this_cpu_inc(irq_stat.spurious_irqs);
+	}
 
 	trace_irq_exit(regs);
 
-- 
2.17.1

[PATCH kernel v4 2/2] powerpc/xive: Drop current cpu priority for orphaned interrupts

[Alexey Kardashevskiy]

There is a race between releasing an irq on one cpu and fetching it
from XIVE on another cpu. When such released irq appears in a queue,
we take it from the queue but we do not change the current priority
on that cpu and since there is no handler for the irq, EOI is never
called and the cpu current priority remains elevated
(7 vs. 0xff==unmasked). If another irq is assigned to the same cpu,
then that device stops working until irq is moved to another cpu or
the device is reset.

This implements ppc_md.orphan_irq callback which is called if no irq
descriptor is found and which drops the current priority
to 0xff which effectively unmasks interrupts in a current CPU.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 arch/powerpc/sysdev/xive/common.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive/common.c
index 082c7e1c20f0..17e696b2d71b 100644
--- a/arch/powerpc/sysdev/xive/common.c
+++ b/arch/powerpc/sysdev/xive/common.c
@@ -283,6 +283,23 @@ static unsigned int xive_get_irq(void)
 	return irq;
 }
 
+/*
+ * Handles the case when a target CPU catches an interrupt which is being shut
+ * down on another CPU. generic_handle_irq() returns an error in such case
+ * and then the orphan_irq() handler restores the CPPR to reenable interrupts.
+ *
+ * Without orphan_irq() and valid irq_desc, there is no other way to restore
+ * the CPPR. This executes on a CPU which caught the interrupt.
+ */
+static void xive_orphan_irq(unsigned int irq)
+{
+	struct xive_cpu *xc = __this_cpu_read(xive_cpu);
+
+	xc->cppr = 0xff;
+	out_8(xive_tima + xive_tima_offset + TM_CPPR, 0xff);
+	DBG_VERBOSE("orphan_irq: irq %d, adjusting CPPR to 0xff\n", irq);
+}
+
 /*
  * After EOI'ing an interrupt, we need to re-check the queue
  * to see if another interrupt is pending since multiple
@@ -1419,6 +1436,7 @@ bool __init xive_core_init(const struct xive_ops *ops, void __iomem *area, u32 o
 	xive_irq_priority = max_prio;
 
 	ppc_md.get_irq = xive_get_irq;
+	ppc_md.orphan_irq = xive_orphan_irq;
 	__xive_enabled = true;
 
 	pr_devel("Initializing host..\n");
-- 
2.17.1