linux-kernel - Re: [PATCH v2] powerpc/xive: Fix bogus error code returned by OPAL

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Message-ID: <a15c02b2-ac3a-21a7-db56-242cb864f79e@kaod.org>
Date:   Wed, 11 Sep 2019 18:02:10 +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 v2] powerpc/xive: Fix bogus error code returned by OPAL

On 11/09/2019 17:52, 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
> in the field.
> 
> Internally convert 0xffffffff to OPAL_RESOURCE which is the usual error
> returned upon resource exhaustion.
> 
> Cc: stable@...r.kernel.org # v4.12+
> Signed-off-by: Greg Kurz <groug@...d.org>



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

Thanks,

C.

> ---
> v2: - fix syntax error in changelog
>     - Cc stable
>     - rename original OPAL wrapper
>     - rewrite fixup wrapper (style, use s64 and u32)
> ---
>  arch/powerpc/include/asm/opal.h            |    2 +-
>  arch/powerpc/platforms/powernv/opal-call.c |    2 +-
>  arch/powerpc/sysdev/xive/native.c          |   11 +++++++++++
>  3 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
> index 57bd029c715e..d5a0807d21db 100644
> --- a/arch/powerpc/include/asm/opal.h
> +++ b/arch/powerpc/include/asm/opal.h
> @@ -272,7 +272,7 @@ int64_t opal_xive_get_vp_info(uint64_t vp,
>  int64_t opal_xive_set_vp_info(uint64_t vp,
>  			      uint64_t flags,
>  			      uint64_t report_cl_pair);
> -int64_t opal_xive_allocate_irq(uint32_t chip_id);
> +int64_t opal_xive_allocate_irq_raw(uint32_t chip_id);
>  int64_t opal_xive_free_irq(uint32_t girq);
>  int64_t opal_xive_sync(uint32_t type, uint32_t id);
>  int64_t opal_xive_dump(uint32_t type, uint32_t id);
> diff --git a/arch/powerpc/platforms/powernv/opal-call.c b/arch/powerpc/platforms/powernv/opal-call.c
> index 29ca523c1c79..dccdc9df5213 100644
> --- a/arch/powerpc/platforms/powernv/opal-call.c
> +++ b/arch/powerpc/platforms/powernv/opal-call.c
> @@ -257,7 +257,7 @@ OPAL_CALL(opal_xive_set_queue_info,		OPAL_XIVE_SET_QUEUE_INFO);
>  OPAL_CALL(opal_xive_donate_page,		OPAL_XIVE_DONATE_PAGE);
>  OPAL_CALL(opal_xive_alloc_vp_block,		OPAL_XIVE_ALLOCATE_VP_BLOCK);
>  OPAL_CALL(opal_xive_free_vp_block,		OPAL_XIVE_FREE_VP_BLOCK);
> -OPAL_CALL(opal_xive_allocate_irq,		OPAL_XIVE_ALLOCATE_IRQ);
> +OPAL_CALL(opal_xive_allocate_irq_raw,		OPAL_XIVE_ALLOCATE_IRQ);
>  OPAL_CALL(opal_xive_free_irq,			OPAL_XIVE_FREE_IRQ);
>  OPAL_CALL(opal_xive_get_vp_info,		OPAL_XIVE_GET_VP_INFO);
>  OPAL_CALL(opal_xive_set_vp_info,		OPAL_XIVE_SET_VP_INFO);
> diff --git a/arch/powerpc/sysdev/xive/native.c b/arch/powerpc/sysdev/xive/native.c
> index 37987c815913..ad8ee7dd7f57 100644
> --- a/arch/powerpc/sysdev/xive/native.c
> +++ b/arch/powerpc/sysdev/xive/native.c
> @@ -231,6 +231,17 @@ static bool xive_native_match(struct device_node *node)
>  	return of_device_is_compatible(node, "ibm,opal-xive-vc");
>  }
>  
> +static s64 opal_xive_allocate_irq(u32 chip_id)
> +{
> +	s64 irq = opal_xive_allocate_irq_raw(chip_id);
> +
> +	/*
> +	 * Old versions of skiboot can incorrectly return 0xffffffff to
> +	 * indicate no space, fix it up here.
> +	 */
> +	return irq == 0xffffffff ? OPAL_RESOURCE : irq;
> +}
> +
>  #ifdef CONFIG_SMP
>  static int xive_native_get_ipi(unsigned int cpu, struct xive_cpu *xc)
>  {
>