Re: [PATCH v1 07/10] powerpc/pseries/iommu: Allow DDW windows starting at 0x00

Alexey Kardashevskiy
2020-08-24T03:44:20Z

On 18/08/2020 09:40, Leonardo Bras wrote:
> enable_ddw() currently returns the address of the DMA window, which is
> considered invalid if has the value 0x00.
>
> Also, it only considers valid an address returned from find_existing_ddw
> if it's not 0x00.
>
> Changing this behavior makes sense, given the users of enable_ddw() only
> need to know if direct mapping is possible. It can also allow a DMA window
> starting at 0x00 to be used.
>
> This will be helpful for using a DDW with indirect mapping, as the window
> address will be different than 0x00, but it will not map the whole
> partition.
>
> Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
> ---
> arch/powerpc/platforms/pseries/iommu.c | 30 ++++++++++++--------------
> 1 file changed, 14 insertions(+), 16 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> index fcdefcc0f365..4031127c9537 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -852,24 +852,25 @@ static void remove_ddw(struct device_node *np, bool remove_prop)
> np, ret);
> }
>
> -static u64 find_existing_ddw(struct device_node *pdn)
> +static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr)
> {
> struct direct_window *window;
> const struct dynamic_dma_window_prop *direct64;
> - u64 dma_addr = 0;
> + bool found = false;
>
> spin_lock(&direct_window_list_lock);
> /* check if we already created a window and dupe that config if so */
> list_for_each_entry(window, &direct_window_list, list) {
> if (window->device == pdn) {
> direct64 = window->prop;
> - dma_addr = be64_to_cpu(direct64->dma_base);
> + *dma_addr = be64_to_cpu(direct64->dma_base);
> + found = true;
> break;
> }
> }
> spin_unlock(&direct_window_list_lock);
>
> - return dma_addr;
> + return found;
> }
>
> static struct direct_window *ddw_list_add(struct device_node *pdn,
> @@ -1131,15 +1132,15 @@ static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn)
> * pdn: the parent pe node with the ibm,dma_window property
> * Future: also check if we can remap the base window for our base page size
> *
> - * returns the dma offset for use by the direct mapped DMA code.
> + * returns true if can map all pages (direct mapping), false otherwise..
> */
> -static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
> +static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn)
> {
> int len, ret;
> struct ddw_query_response query;
> struct ddw_create_response create;
> int page_shift;
> - u64 dma_addr, max_addr;
> + u64 max_addr;
> struct device_node *dn;
> u32 ddw_avail[DDW_APPLICABLE_SIZE];
> struct direct_window *window;
> @@ -1150,8 +1151,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>
> mutex_lock(&direct_window_init_mutex);
>
> - dma_addr = find_existing_ddw(pdn);
> - if (dma_addr != 0)
> + if (find_existing_ddw(pdn, &dev->dev.archdata.dma_offset))
> goto out_unlock;
>
> /*
> @@ -1292,7 +1292,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
> goto out_free_window;
> }
>
> - dma_addr = be64_to_cpu(ddwprop->dma_base);
> + dev->dev.archdata.dma_offset = be64_to_cpu(ddwprop->dma_base);

Do not you need the same chunk in the find_existing_ddw() case above as
well? Thanks,

> goto out_unlock;
>
> out_free_window:
> @@ -1309,6 +1309,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
> kfree(win64->name);
> kfree(win64->value);
> kfree(win64);
> + win64 = NULL;
>
> out_failed:
> if (default_win_removed)
> @@ -1322,7 +1323,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>
> out_unlock:
> mutex_unlock(&direct_window_init_mutex);
> - return dma_addr;
> + return win64;
> }
>
> static void pci_dma_dev_setup_pSeriesLP(struct pci_dev *dev)
> @@ -1401,11 +1402,8 @@ static bool iommu_bypass_supported_pSeriesLP(struct pci_dev *pdev, u64 dma_mask)
> break;
> }
>
> - if (pdn && PCI_DN(pdn)) {
> - pdev->dev.archdata.dma_offset = enable_ddw(pdev, pdn);
> - if (pdev->dev.archdata.dma_offset)
> - return true;
> - }
> + if (pdn && PCI_DN(pdn))
> + return enable_ddw(pdev, pdn);
>
> return false;
> }
>

--
Alexey