Re: [PATCH] powerpc/xive: Fix bogus error code returned by OPAL

On Thu, 12 Sep 2019 00:26:19 +1000
Michael Ellerman [off-list ref] wrote:

Hi Greg,

Bom dia ! :)

Couple of comments ...

Greg Kurz [off-list ref] writes:

quoted

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.

  ^
  in
 

quoted

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

This should go to stable, any idea what versions it should go back to?
Probably whenever the xive code was introduced?

Yes I guess so. This would mean v4.12. I'll add the appropriate stable
tag before re-posting, and address all the other remarks of course.

quoted

Signed-off-by: Greg Kurz <redacted>
---
 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)

          ^                                    ^
          Can you use s64 here and u32 here ....

Instead of calling this opal_xive_allocate_irq_fixup() and relying on
all callers to call the fixup, can we rename the opal wrapper and leave
this function's name unchanged, eg:

-OPAL_CALL(opal_xive_allocate_irq,              OPAL_XIVE_ALLOCATE_IRQ);
+OPAL_CALL(opal_xive_allocate_irq_raw,          OPAL_XIVE_ALLOCATE_IRQ);

quoted

+{
+	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;
+}

I don't really like the #define and the weird indenting and so on, can
we instead do it like:

	/*
         * Old versions of skiboot can incorrectly return 0xffffffff to
         * indicate no space, fix it up here.
         */
	return irq == 0xffffffff ? OPAL_RESOURCE : irq;

cheers