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

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Message-ID: <b8c656c8-296c-2bc3-0758-ca513e76a19f@kaod.org>
Date:   Tue, 10 Sep 2019 15:59:37 +0200
From:   Cédric Le Goater <clg@...d.org>
To:     Greg Kurz <groug@...d.org>, Michael Ellerman <mpe@...erman.id.au>
Cc:     Paul Mackerras <paulus@...abs.org>,
        David Gibson <david@...son.dropbear.id.au>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/xive: Fix bogus error code returned by OPAL

On 10/09/2019 15:53, Greg Kurz wrote:
> 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>



Reviewed-by: Cédric Le Goater <clg@...d.org>

Thanks,

C.

> ---
>  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);
>