linux-kernel - [PATCH] powerpc/xive: Fix bogus error code returned by OPAL

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Date:   Tue, 10 Sep 2019 15:53:45 +0200
From:   Greg Kurz <groug@...d.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Paul Mackerras <paulus@...abs.org>,
        Cédric Le Goater <clg@...d.org>,
        David Gibson <david@...son.dropbear.id.au>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH] powerpc/xive: Fix bogus error code returned by OPAL

There's a bug in skiboot that causes the OPAL_XIVE_ALLOCATE_IRQ call
to return the 32-bit value 0xffffffff when OPAL has run out of IRQs.
Unfortunatelty, OPAL return values are signed 64-bit entities and
errors are supposed to be negative. If that happens, the linux code
confusingly treats 0xffffffff as a valid IRQ number and panics at some
point.

A fix was recently merged in skiboot:

e97391ae2bb5 ("xive: fix return value of opal_xive_allocate_irq()")

but we need a workaround anyway to support older skiboots already
on the field.

Internally convert 0xffffffff to OPAL_RESOURCE which is the usual error
returned upon resource exhaustion.

Signed-off-by: Greg Kurz <groug@...d.org>
---
 arch/powerpc/sysdev/xive/native.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/sysdev/xive/native.c b/arch/powerpc/sysdev/xive/native.c
index 37987c815913..c35583f84f9f 100644
--- a/arch/powerpc/sysdev/xive/native.c
+++ b/arch/powerpc/sysdev/xive/native.c
@@ -231,6 +231,15 @@ static bool xive_native_match(struct device_node *node)
 	return of_device_is_compatible(node, "ibm,opal-xive-vc");
 }
 
+static int64_t opal_xive_allocate_irq_fixup(uint32_t chip_id)
+{
+	s64 irq = opal_xive_allocate_irq(chip_id);
+
+#define XIVE_ALLOC_NO_SPACE	0xffffffff /* No possible space */
+	return
+		irq == XIVE_ALLOC_NO_SPACE ? OPAL_RESOURCE : irq;
+}
+
 #ifdef CONFIG_SMP
 static int xive_native_get_ipi(unsigned int cpu, struct xive_cpu *xc)
 {
@@ -238,7 +247,7 @@ static int xive_native_get_ipi(unsigned int cpu, struct xive_cpu *xc)
 
 	/* Allocate an IPI and populate info about it */
 	for (;;) {
-		irq = opal_xive_allocate_irq(xc->chip_id);
+		irq = opal_xive_allocate_irq_fixup(xc->chip_id);
 		if (irq == OPAL_BUSY) {
 			msleep(OPAL_BUSY_DELAY_MS);
 			continue;
@@ -259,7 +268,7 @@ u32 xive_native_alloc_irq(void)
 	s64 rc;
 
 	for (;;) {
-		rc = opal_xive_allocate_irq(OPAL_XIVE_ANY_CHIP);
+		rc = opal_xive_allocate_irq_fixup(OPAL_XIVE_ANY_CHIP);
 		if (rc != OPAL_BUSY)
 			break;
 		msleep(OPAL_BUSY_DELAY_MS);