linux-kernel - Re: [PATCH] of/irq: Fix msi-map calculation for nonzero rid-base

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Date:	Tue, 9 Feb 2016 12:06:06 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Robin Murphy <robin.murphy@....com>, robh+dt@...nel.org,
	frowand.list@...il.com, grant.likely@...aro.org,
	devicetree@...r.kernel.org
Cc:	mark.rutland@....com, david.daney@...ium.com, stuart.yoder@....com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] of/irq: Fix msi-map calculation for nonzero rid-base

Hi Robin,

On 09/02/16 11:04, Robin Murphy wrote:
> The existing msi-map code is fine for shifting the entire RID space
> upwards, but attempting finer-grained remapping reveals a bug. It turns
> out that we are mistakenly treating the msi-base part as an offset, not
> as a new base to remap onto, so things get squiffy when rid-base is
> nonzero. Fix this, and at the same time add a sanity check against
> having msi-map-mask clash with a nonzero rid-base, as that's another
> thing one can easily get wrong.
> 
> CC: <stable@...r.kernel.org>
> Signed-off-by: Robin Murphy <robin.murphy@....com>

Looks like Stuart and you both found the same bug at the same time:
https://lkml.org/lkml/2016/2/8/1066

but yours seem more correct to me (the rid_base masking in Stuart's
version seems odd).

> ---
>  drivers/of/irq.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/of/irq.c b/drivers/of/irq.c
> index 7ee21ae..e7bfc17 100644
> --- a/drivers/of/irq.c
> +++ b/drivers/of/irq.c
> @@ -635,6 +635,13 @@ static u32 __of_msi_map_rid(struct device *dev, struct device_node **np,
>  		msi_base = be32_to_cpup(msi_map + 2);
>  		rid_len = be32_to_cpup(msi_map + 3);
>  
> +		if (rid_base & ~map_mask) {
> +			dev_err(parent_dev,
> +				"Invalid msi-map translation - msi-map-mask (0x%x) ignores rid-base (0x%x)\n",
> +				map_mask, rid_base);
> +			return rid_out;
> +		}
> +
>  		msi_controller_node = of_find_node_by_phandle(phandle);
>  
>  		matched = (masked_rid >= rid_base &&
> @@ -654,7 +661,7 @@ static u32 __of_msi_map_rid(struct device *dev, struct device_node **np,
>  	if (!matched)
>  		return rid_out;
>  
> -	rid_out = masked_rid + msi_base;
> +	rid_out = masked_rid - rid_base + msi_base;
>  	dev_dbg(dev,
>  		"msi-map at: %s, using mask %08x, rid-base: %08x, msi-base: %08x, length: %08x, rid: %08x -> %08x\n",
>  		dev_name(parent_dev), map_mask, rid_base, msi_base,
> 

Reviewed-by: Marc Zyngier <marc.zyngier@....com>

	M.
-- 
Jazz is not dead. It just smells funny...