Subject: Re: [PATCH] powerpc: EOI spurious irqs during boot so they can be reenabled later

From: Michael Ellerman <[email-masked]>
Date: Wed, 06 Aug 2008 14:53:54 +1000

On Tue, 2008-08-05 at 20:55 -0600, miltonm wrote:
> ----- Original Message Follows -----
> From: Michael Ellerman <[email-masked]>
> To: Paul Mackerras <[email-masked]>
> Cc: <[email-masked]>, Milton Miller
> <[email-masked]>, Segher Boessenkool
> <[email-masked]>
> Subject: [PATCH] powerpc: EOI spurious irqs during boot so
> they can be reenabled later
> Date: Wed,  6 Aug 2008 12:03:37 +1000 (EST)
>  
> > In the xics code, if we receive an irq during boot that
> > hasn't been setup yet - ie. we have no reverse mapping for
> > it - we mask the irq so we don't hear from it again.
> > 
> > Later on if someone request_irq()'s that irq, we'll unmask
> > it but it will still never fire. This is because we never
> > EOI'ed the irq when we originally received it - when it
> > was spurious.
> > 
> > This can be reproduced trivially by banging the keyboard
> > while kexec'ing on a P5 LPAR, even though the hvc_console
> > driver request's the console irq, the console is
> > non-functional because we're receiving no console
> > interrupts.
> > 
>  
> which means some driver didn't disable interrupts on its
> shutdown, but I digress.

But in the case of kdump the driver never gets a chance to shutdown its
irq, but I digress too :)

> > diff --git a/arch/powerpc/platforms/pseries/xics.c
> > b/arch/powerpc/platforms/pseries/xics.c index
> > 0fc830f..4c692b2 100644 ---
> > a/arch/powerpc/platforms/pseries/xics.c +++
> > b/arch/powerpc/platforms/pseries/xics.c @@ -321,21 +321,26
> > @@ static unsigned int xics_startup(unsigned int virq)
> >      return 0;
> >  }
> >  
> > +static void xics_eoi_hwirq_direct(unsigned int hwirq)
> > +{
> > +    iosync();
> > +    direct_xirr_info_set((0xff << 24) | hwirq);
> > +}
> > +
> >  static void xics_eoi_direct(unsigned int virq)
> >  {
> > -    unsigned int irq = (unsigned int)irq_map[virq].hwirq;
> > +    xics_eoi_hwirq_direct((unsigned
> > int)irq_map[virq].hwirq); +}
> >  
> > +static void xics_eoi_hwirq_lpar(unsigned int hwirq)
> > +{
> >      iosync();
> > -    direct_xirr_info_set((0xff << 24) | irq);
> > +    lpar_xirr_info_set((0xff << 24) | hwirq);
> >  }
> >  
> > -
> >  static void xics_eoi_lpar(unsigned int virq)
> >  {
> > -    unsigned int irq = (unsigned int)irq_map[virq].hwirq;
> > -
> > -    iosync();
> > -    lpar_xirr_info_set((0xff << 24) | irq);
> > +    xics_eoi_hwirq_lpar((unsigned
> > int)irq_map[virq].hwirq);
> >  }
> >  
> >  static inline unsigned int xics_remap_irq(unsigned int
> > vec) @@ -350,9 +355,15 @@ static inline unsigned int
> > xics_remap_irq(unsigned int vec)
> >      if (likely(irq != NO_IRQ))
> >          return irq;
> >  
> > -    printk(KERN_ERR "Interrupt %u (real) is invalid,"
> > -           " disabling it.\n", vec);
> > +    pr_err("%s: no mapping for hwirq %u, disabling it.\n"
> > , __func__, vec); +
> >      xics_mask_real_irq(vec);
> > +
> > +    if (firmware_has_feature(FW_FEATURE_LPAR))
> > +        xics_eoi_hwirq_lpar(vec);
> > +    else
> > +        xics_eoi_hwirq_direct(vec);
> > +
> >      return NO_IRQ;
> >  }
>  
> 
> I really dislike this great big if in the middle of a
> function.
> we called this function from two different call sites where
> the
> choice of which to call was based on their environment.
>  
> Please move the call to eoi the hwirq to the callers, who
> know which path to take.

It's not pretty, but the alternative is worse I think:

>>From 0a908825c8de6cd4c26288aba8c5b7fe3ed0a69f Mon Sep 17 00:00:00 2001
From: Michael Ellerman <[email-masked]>
Date: Tue, 5 Aug 2008 22:34:48 +1000
Subject: [PATCH] powerpc: EOI spurious irqs during boot so they can be reenabled later

In the xics code, if we receive an irq during boot that hasn't been setup
yet - ie. we have no reverse mapping for it - we mask the irq so we don't
hear from it again.

Later on if someone request_irq()'s that irq, we'll unmask it but it will
still never fire. This is because we never EOI'ed the irq when we originally
received it - when it was spurious.

This can be reproduced trivially by banging the keyboard while kexec'ing on
a P5 LPAR, even though the hvc_console driver request's the console irq, the
console is non-functional because we're receiving no console interrupts.

So when we receive a spurious irq mask it and then EOI it.

Signed-off-by: Michael Ellerman <[email-masked]>
---
 arch/powerpc/platforms/pseries/xics.c |   74 ++++++++++++++++++++++-----------
 1 files changed, 50 insertions(+), 24 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/xics.c b/arch/powerpc/platforms/pseries/xics.c
index 0fc830f..754706c 100644
--- a/arch/powerpc/platforms/pseries/xics.c
+++ b/arch/powerpc/platforms/pseries/xics.c
@@ -90,7 +90,7 @@ static inline unsigned int direct_xirr_info_get(void)
 {
 	int cpu = smp_processor_id();
 
-	return in_be32(&xics_per_cpu[cpu]->xirr.word);
+	return in_be32(&xics_per_cpu[cpu]->xirr.word) & 0x00ffffff;
 }
 
 static inline void direct_xirr_info_set(int value)
@@ -124,7 +124,8 @@ static inline unsigned int lpar_xirr_info_get(void)
 	lpar_rc = plpar_xirr(&return_value);
 	if (lpar_rc != H_SUCCESS)
 		panic(" bad return code xirr - rc = %lx \n", lpar_rc);
-	return (unsigned int)return_value;
+
+	return (unsigned int)return_value & 0x00ffffff;
 }
 
 static inline void lpar_xirr_info_set(int value)
@@ -321,49 +322,74 @@ static unsigned int xics_startup(unsigned int virq)
 	return 0;
 }
 
+static void xics_eoi_hwirq_direct(unsigned int hwirq)
+{
+	iosync();
+	direct_xirr_info_set((0xff << 24) | hwirq);
+}
+
 static void xics_eoi_direct(unsigned int virq)
 {
-	unsigned int irq = (unsigned int)irq_map[virq].hwirq;
+	xics_eoi_hwirq_direct((unsigned int)irq_map[virq].hwirq);
+}
 
+static void xics_eoi_hwirq_lpar(unsigned int hwirq)
+{
 	iosync();
-	direct_xirr_info_set((0xff << 24) | irq);
+	lpar_xirr_info_set((0xff << 24) | hwirq);
 }
 
-
 static void xics_eoi_lpar(unsigned int virq)
 {
-	unsigned int irq = (unsigned int)irq_map[virq].hwirq;
-
-	iosync();
-	lpar_xirr_info_set((0xff << 24) | irq);
+	xics_eoi_hwirq_lpar((unsigned int)irq_map[virq].hwirq);
 }
 
 static inline unsigned int xics_remap_irq(unsigned int vec)
 {
-	unsigned int irq;
-
-	vec &= 0x00ffffff;
-
-	if (vec == XICS_IRQ_SPURIOUS)
-		return NO_IRQ;
-	irq = irq_radix_revmap(xics_host, vec);
-	if (likely(irq != NO_IRQ))
-		return irq;
+	return irq_radix_revmap(xics_host, vec);
+}
 
-	printk(KERN_ERR "Interrupt %u (real) is invalid,"
-	       " disabling it.\n", vec);
-	xics_mask_real_irq(vec);
-	return NO_IRQ;
+static void xics_report_bad_irq(unsigned int hwirq)
+{
+	pr_err("%s: no mapping for hwirq %u, disabling it.\n", __func__, hwirq);
 }
 
 static unsigned int xics_get_irq_direct(void)
 {
-	return xics_remap_irq(direct_xirr_info_get());
+	unsigned int virq, hwirq;
+
+	hwirq = direct_xirr_info_get();
+	if (hwirq == XICS_IRQ_SPURIOUS)
+		return NO_IRQ;
+
+	virq = xics_remap_irq(hwirq);
+
+	if (unlikely(virq == NO_IRQ)) {
+		xics_report_bad_irq(hwirq);
+		xics_mask_real_irq(hwirq);
+		xics_eoi_hwirq_direct(hwirq);
+	}
+
+	return virq;
 }
 
 static unsigned int xics_get_irq_lpar(void)
 {
-	return xics_remap_irq(lpar_xirr_info_get());
+	unsigned int virq, hwirq;
+
+	hwirq = lpar_xirr_info_get();
+	if (hwirq == XICS_IRQ_SPURIOUS)
+		return NO_IRQ;
+
+	virq = xics_remap_irq(hwirq);
+
+	if (unlikely(virq == NO_IRQ)) {
+		xics_report_bad_irq(hwirq);
+		xics_mask_real_irq(hwirq);
+		xics_eoi_hwirq_lpar(hwirq);
+	}
+
+	return virq;
 }
 
 #ifdef CONFIG_SMP
-- 
1.5.5