linux-kernel - Re: [PATCH v4 09/11] powerpc/pseries/iommu: Find existing DDW with given property name

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Message-ID: <8055abc8-ed12-b054-7683-cd80fe0d59de@ozlabs.ru>
Date:   Tue, 11 May 2021 17:57:33 +1000
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     Leonardo Bras <leobras.c@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Joel Stanley <joel@....id.au>,
        Christophe Leroy <christophe.leroy@....fr>,
        Nicolin Chen <nicoleotsuka@...il.com>,
        Niklas Schnelle <schnelle@...ux.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 09/11] powerpc/pseries/iommu: Find existing DDW with
 given property name



On 01/05/2021 02:31, Leonardo Bras wrote:
> At the moment pseries stores information about created directly mapped
> DDW window in DIRECT64_PROPNAME.
> 
> With the objective of implementing indirect DMA mapping with DDW, it's
> necessary to have another propriety name to make sure kexec'ing into older
> kernels does not break, as it would if we reuse DIRECT64_PROPNAME.
> 
> In order to have this, find_existing_ddw_windows() needs to be able to
> look for different property names.
> 
> Extract find_existing_ddw_windows() into find_existing_ddw_windows_named()
> and calls it with current property name.
> 
> Signed-off-by: Leonardo Bras <leobras.c@...il.com>
> ---
>   arch/powerpc/platforms/pseries/iommu.c | 25 +++++++++++++++----------
>   1 file changed, 15 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> index f8922fcf34b6..de54ddd9decd 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -888,24 +888,21 @@ static struct direct_window *ddw_list_new_entry(struct device_node *pdn,
>   	return window;
>   }
>   
> -static int find_existing_ddw_windows(void)
> +static void find_existing_ddw_windows_named(const char *name)

I'd suggest find_existing_ddw_windows_by_name() but this is nitpicking.

Reviewed-by: Alexey Kardashevskiy <aik@...abs.ru>


>   {
>   	int len;
>   	struct device_node *pdn;
>   	struct direct_window *window;
> -	const struct dynamic_dma_window_prop *direct64;
> -
> -	if (!firmware_has_feature(FW_FEATURE_LPAR))
> -		return 0;
> +	const struct dynamic_dma_window_prop *dma64;
>   
> -	for_each_node_with_property(pdn, DIRECT64_PROPNAME) {
> -		direct64 = of_get_property(pdn, DIRECT64_PROPNAME, &len);
> -		if (!direct64 || len < sizeof(*direct64)) {
> -			remove_ddw(pdn, true, DIRECT64_PROPNAME);
> +	for_each_node_with_property(pdn, name) {
> +		dma64 = of_get_property(pdn, name, &len);
> +		if (!dma64 || len < sizeof(*dma64)) {
> +			remove_ddw(pdn, true, name);
>   			continue;
>   		}
>   
> -		window = ddw_list_new_entry(pdn, direct64);
> +		window = ddw_list_new_entry(pdn, dma64);
>   		if (!window)
>   			break;
>   
> @@ -913,6 +910,14 @@ static int find_existing_ddw_windows(void)
>   		list_add(&window->list, &direct_window_list);
>   		spin_unlock(&direct_window_list_lock);
>   	}
> +}
> +
> +static int find_existing_ddw_windows(void)
> +{
> +	if (!firmware_has_feature(FW_FEATURE_LPAR))
> +		return 0;
> +
> +	find_existing_ddw_windows_named(DIRECT64_PROPNAME);
>   
>   	return 0;
>   }
> 

-- 
Alexey