On 05/08/2020 13:04, Leonardo Bras wrote:
> On LoPAR "DMA Window Manipulation Calls", it's recommended to remove the
> default DMA window for the device, before attempting to configure a DDW,
> in order to make the maximum resources available for the next DDW to be
> created.
>
> This is a requirement for using DDW on devices in which hypervisor
> allows only one DMA window.
>
> If setting up a new DDW fails anywhere after the removal of this
> default DMA window, it's needed to restore the default DMA window.
> For this, an implementation of ibm,reset-pe-dma-windows rtas call is
> needed:
>
> Platforms supporting the DDW option starting with LoPAR level 2.7 implement
> ibm,ddw-extensions. The first extension available (index 2) carries the
> token for ibm,reset-pe-dma-windows rtas call, which is used to restore
> the default DMA window for a device, if it has been deleted.
>
> It does so by resetting the TCE table allocation for the PE to it's
> boot time value, available in "ibm,dma-window" device tree node.
>
> Signed-off-by: Leonardo Bras <leobra...@gmail.com>
> Tested-by: David Dai <z...@linux.vnet.ibm.com>
Reviewed-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> ---
> arch/powerpc/platforms/pseries/iommu.c | 73 +++++++++++++++++++++++---
> 1 file changed, 66 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/iommu.c
> b/arch/powerpc/platforms/pseries/iommu.c
> index 4e33147825cc..e4198700ed1a 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -1066,6 +1066,38 @@ static phys_addr_t ddw_memory_hotplug_max(void)
> return max_addr;
> }
>
> +/*
> + * Platforms supporting the DDW option starting with LoPAR level 2.7
> implement
> + * ibm,ddw-extensions, which carries the rtas token for
> + * ibm,reset-pe-dma-windows.
> + * That rtas-call can be used to restore the default DMA window for the
> device.
> + */
> +static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn)
> +{
> + int ret;
> + u32 cfg_addr, reset_dma_win;
> + u64 buid;
> + struct device_node *dn;
> + struct pci_dn *pdn;
> +
> + ret = ddw_read_ext(par_dn, DDW_EXT_RESET_DMA_WIN, &reset_dma_win);
> + if (ret)
> + return;
> +
> + dn = pci_device_to_OF_node(dev);
> + pdn = PCI_DN(dn);
> + buid = pdn->phb->buid;
> + cfg_addr = (pdn->busno << 16) | (pdn->devfn << 8);
> +
> + ret = rtas_call(reset_dma_win, 3, 1, NULL, cfg_addr, BUID_HI(buid),
> + BUID_LO(buid));
> + if (ret)
> + dev_info(&dev->dev,
> + "ibm,reset-pe-dma-windows(%x) %x %x %x returned %d ",
> + reset_dma_win, cfg_addr, BUID_HI(buid), BUID_LO(buid),
> + ret);
> +}
> +
> /*
> * If the PE supports dynamic dma windows, and there is space for a table
> * that can map all pages in a linear offset, then setup such a table,
> @@ -1090,6 +1122,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct
> device_node *pdn)
> struct property *win64;
> struct dynamic_dma_window_prop *ddwprop;
> struct failed_ddw_pdn *fpdn;
> + bool default_win_removed = false;
>
> mutex_lock(&direct_window_init_mutex);
>
> @@ -1133,14 +1166,38 @@ static u64 enable_ddw(struct pci_dev *dev, struct
> device_node *pdn)
> if (ret != 0)
> goto out_failed;
>
> + /*
> + * If there is no window available, remove the default DMA window,
> + * if it's present. This will make all the resources available to the
> + * new DDW window.
> + * If anything fails after this, we need to restore it, so also check
> + * for extensions presence.
> + */
> if (query.windows_available == 0) {
> - /*
> - * no additional windows are available for this device.
> - * We might be able to reallocate the existing window,
> - * trading in for a larger page size.
> - */
> - dev_dbg(&dev->dev, "no free dynamic windows");
> - goto out_failed;
> + struct property *default_win;
> + int reset_win_ext;
> +
> + default_win = of_find_property(pdn, "ibm,dma-window", NULL);
> + if (!default_win)
> + goto out_failed;
> +
> + reset_win_ext = ddw_read_ext(pdn, DDW_EXT_RESET_DMA_WIN, NULL);
> + if (reset_win_ext)
> + goto out_failed;
> +
> + remove_dma_window(pdn, ddw_avail, default_win);
> + default_win_removed = true;
> +
> + /* Query again, to check if the window is available */
> + ret = query_ddw(dev, ddw_avail, &query, pdn);
> + if (ret != 0)
> + goto out_failed;
> +
> + if (query.windows_available == 0) {
> + /* no windows are available for this device. */
> + dev_dbg(&dev->dev, "no free dynamic windows");
> + goto out_failed;
> + }
> }
> if (query.page_size & 4) {
> page_shift = 24; /* 16MB */
> @@ -1231,6 +1288,8 @@ static u64 enable_ddw(struct pci_dev *dev, struct
> device_node *pdn)
> kfree(win64);
>
> out_failed:
> + if (default_win_removed)
> + reset_dma_window(dev, pdn);
>
> fpdn = kzalloc(sizeof(*fpdn), GFP_KERNEL);
> if (!fpdn)
>
--
Alexey
