linux-kernel - Re: [PATCH v2 5/6] powerpc/pseries/iommu: Make use of DDW even if it does not map the partition

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Message-ID: <18df09c0-ef83-a0d8-1143-1cb4d50bf6b7@ozlabs.ru>
Date:   Wed, 1 Jul 2020 18:16:40 +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>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/6] powerpc/pseries/iommu: Make use of DDW even if it
 does not map the partition



On 24/06/2020 16:24, Leonardo Bras wrote:
> As of today, if a DDW is created and can't map the whole partition, it's
> removed and the default DMA window "ibm,dma-window" is used instead.
> 
> Usually this DDW is bigger than the default DMA window, so it would be
> better to make use of it instead.
> 
> Signed-off-by: Leonardo Bras <leobras.c@...il.com>
> ---
>  arch/powerpc/platforms/pseries/iommu.c | 28 +++++++++++++++++---------
>  1 file changed, 19 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> index 4fcf00016fb1..2d217cda4075 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -685,7 +685,7 @@ static void pci_dma_bus_setup_pSeriesLP(struct pci_bus *bus)
>  	struct iommu_table *tbl;
>  	struct device_node *dn, *pdn;
>  	struct pci_dn *ppci;
> -	const __be32 *dma_window = NULL;
> +	const __be32 *dma_window = NULL, *alt_dma_window = NULL;
>  
>  	dn = pci_bus_to_OF_node(bus);
>  
> @@ -699,8 +699,13 @@ static void pci_dma_bus_setup_pSeriesLP(struct pci_bus *bus)
>  			break;
>  	}
>  
> +	/* If there is a DDW available, use it instead */
> +	alt_dma_window = of_get_property(pdn, DIRECT64_PROPNAME, NULL);


It is not necessarily "direct" anymore as the name suggests, you may
want to change that. DMA64_PROPNAME, may be. Thanks,


> +	if (alt_dma_window)
> +		dma_window = alt_dma_window;
> +
>  	if (dma_window == NULL) {
> -		pr_debug("  no ibm,dma-window property !\n");
> +		pr_debug("  no ibm,dma-window nor linux,direct64-ddr-window-info property !\n");
>  		return;
>  	}
>  
> @@ -1166,16 +1171,19 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>  			  query.page_size);
>  		goto out_failed;
>  	}
> +
>  	/* verify the window * number of ptes will map the partition */
> -	/* check largest block * page size > max memory hotplug addr */
>  	max_addr = ddw_memory_hotplug_max();
>  	if (query.largest_available_block < (max_addr >> page_shift)) {
> -		dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu "
> -			  "%llu-sized pages\n", max_addr,  query.largest_available_block,
> -			  1ULL << page_shift);
> -		goto out_failed;
> +		dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu %llu-sized pages\n",
> +			max_addr, query.largest_available_block,
> +			1ULL << page_shift);
> +
> +		len = order_base_2(query.largest_available_block << page_shift);
> +	} else {
> +		len = order_base_2(max_addr);
>  	}
> -	len = order_base_2(max_addr);
> +
>  	win64 = kzalloc(sizeof(struct property), GFP_KERNEL);
>  	if (!win64) {
>  		dev_info(&dev->dev,
> @@ -1229,7 +1237,9 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>  	list_add(&window->list, &direct_window_list);
>  	spin_unlock(&direct_window_list_lock);
>  
> -	dma_addr = be64_to_cpu(ddwprop->dma_base);
> +	/* Only returns the dma_addr if DDW maps the whole partition */
> +	if (len == order_base_2(max_addr))
> +		dma_addr = be64_to_cpu(ddwprop->dma_base);
>  	goto out_unlock;
>  
>  out_free_window:
> 

-- 
Alexey