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

Leonardo Bras
2020-08-28T14:05:36Z

On Mon, 2020-08-24 at 13:44 +1000, Alexey Kardashevskiy wrote:
>
> > 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,

The new signature of find_existing_ddw() is
static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr)

And on enable_ddw(), we call
find_existing_ddw(pdn, &dev->dev.archdata.dma_offset)

And inside the function we do:
*dma_addr = be64_to_cpu(direct64->dma_base);

I think it's the same as the chunk before.
Am I missing something?

>
>
> > 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;
> > }
> >