Re: [PATCH v2] ACPI/IORT: Check node revision for PMCG resources

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Thu, Feb 03, 2022 at 07:31:24PM +0000, Robin Murphy wrote:
> The original version of the IORT PMCG definition had an oversight
> wherein there was no way to describe the second register page for an
> implementation using the recommended RELOC_CTRS feature. Although the
> spec was fixed, and the final patches merged to ACPICA and Linux written
> against the new version, it seems that some old firmware based on the
> original revision has survived and turned up in the wild.
> 
> Add a check for the original PMCG definition, and avoid filling in the
> second memory resource with nonsense if so. Otherwise it is likely that
> something horrible will happen when the PMCG driver attempts to probe.
> 
> Reported-by: Michael Petlan <mpetlan@redhat.com>
> Fixes: 24e516049360 ("ACPI/IORT: Add support for PMCG")
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
> 
> v2: Simpler workaround, since I realised platform_get_resource()
>     should happily just skip over a zero-initialised hole in the
>     resource array.
> 
>  drivers/acpi/arm64/iort.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)

Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

Should we send it to stable kernels ?

I'd kindly ask Catalin/Will to pick it up please.

Thanks,
Lorenzo

> 
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index 175397913be1..7092b94b2aae 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -1371,9 +1371,17 @@ static void __init arm_smmu_v3_pmcg_init_resources(struct resource *res,
>  	res[0].start = pmcg->page0_base_address;
>  	res[0].end = pmcg->page0_base_address + SZ_4K - 1;
>  	res[0].flags = IORESOURCE_MEM;
> -	res[1].start = pmcg->page1_base_address;
> -	res[1].end = pmcg->page1_base_address + SZ_4K - 1;
> -	res[1].flags = IORESOURCE_MEM;
> +	/*
> +	 * The initial version in DEN0049C lacked a way to describe register
> +	 * page 1, which makes it broken for most PMCG implementations; in
> +	 * that case, just let the driver fail gracefully if it expects to
> +	 * find a second memory resource.
> +	 */
> +	if (node->revision > 0) {
> +		res[1].start = pmcg->page1_base_address;
> +		res[1].end = pmcg->page1_base_address + SZ_4K - 1;
> +		res[1].flags = IORESOURCE_MEM;
> +	}
>  
>  	if (pmcg->overflow_gsiv)
>  		acpi_iort_register_irq(pmcg->overflow_gsiv, "overflow",
> -- 
> 2.28.0.dirty
> 

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