Messages in this thread Patch in this message | | | Subject | Re: [PATCH 4/4] powerpc/pseries/iommu: Remove default DMA window before creating DDW | From | Alexey Kardashevskiy <> | Date | Mon, 22 Jun 2020 20:02:51 +1000 |
| |
On 19/06/2020 15:06, 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 some devices to use DDW, given they only > allow one DMA window. > > If setting up a new DDW fails anywhere after the removal of this > default DMA window, restore it using reset_dma_window.
Nah... If we do it like this, then under pHyp we lose 32bit DMA for good as pHyp can only create a single window and it has to map at 0x800.0000.0000.0000. They probably do not care though.
Under KVM, this will fail as VFIO allows creating 2 windows and it starts from 0 but the existing iommu_bypass_supported_pSeriesLP() treats the window address == 0 as a failure. And we want to keep both DMA windows for PCI adapters with both 64bit and 32bit PCI functions (I heard AMD GPU video + audio are like this) or someone could hotplug 32bit DMA device on a vphb with already present 64bit DMA window so we do not remove the default window.
The last discussed thing I remember was that there was supposed to be a new bit in "ibm,architecture-vec-5" (forgot the details), we could use that to decide whether to keep the default window or not, like this.
> > Signed-off-by: Leonardo Bras <leobras.c@gmail.com> > --- > arch/powerpc/platforms/pseries/iommu.c | 20 +++++++++++++++++--- > 1 file changed, 17 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c > index de633f6ae093..68d1ea957ac7 100644 > --- a/arch/powerpc/platforms/pseries/iommu.c > +++ b/arch/powerpc/platforms/pseries/iommu.c > @@ -1074,8 +1074,9 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) > u64 dma_addr, max_addr; > struct device_node *dn; > u32 ddw_avail[3]; > + > struct direct_window *window; > - struct property *win64; > + struct property *win64, *dfl_win;
Make it "default_win" or "def_win", "dfl" hurts to read :)
> struct dynamic_dma_window_prop *ddwprop; > struct failed_ddw_pdn *fpdn; > > @@ -1110,8 +1111,19 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) > if (ret) > goto out_failed; > > - /* > - * Query if there is a second window of size to map the > + /* > + * First step of setting up DDW is removing the default DMA window, > + * if it's present. It will make all the resources available to the > + * new DDW window. > + * If anything fails after this, we need to restore it. > + */ > + > + dfl_win = of_find_property(pdn, "ibm,dma-window", NULL); > + if (dfl_win) > + remove_dma_window(pdn, ddw_avail, dfl_win);
Before doing so, you want to make sure that the "reset" is actually supported. Thanks,
> + > + /* > + * Query if there is a window of size to map the > * whole partition. Query returns number of windows, largest > * block assigned to PE (partition endpoint), and two bitmasks > * of page sizes: supported and supported for migrate-dma. > @@ -1219,6 +1231,8 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) > kfree(win64); > > out_failed: > + if (dfl_win) > + reset_dma_window(dev, pdn); > > fpdn = kzalloc(sizeof(*fpdn), GFP_KERNEL); > if (!fpdn) >
-- Alexey
| |