Re: [PATCH v5 3/7] PCI: Introduce pci_real_dma_dev()

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Wed, Jan 22, 2020 at 03:12:59PM -0600, Bjorn Helgaas wrote:
> On Tue, Jan 21, 2020 at 06:37:47AM -0700, Jon Derrick wrote:
> > The current DMA alias implementation requires the aliased device be on
> > the same PCI bus as the requester ID. This introduces an arch-specific
> > mechanism to point to another PCI device when doing mapping and
> > PCI DMA alias search. The default case returns the actual device.
> > 
> > CC: Christoph Hellwig <hch@lst.de>
> > Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
> 
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
> 
> Looks like a nice cleanup to me.
> 
> Lorenzo, let me know if you want me to take this.

Hi Bjorn,

I think it makes sense for you to take the series given that
it is mostly core/x86 changes. FWIW I Acked the relevant patch
(6) even though Jon forgot to carry it to v5.

Thanks,
Lorenzo

> >  arch/x86/pci/common.c | 10 ++++++++++
> >  drivers/pci/pci.c     | 19 ++++++++++++++++++-
> >  drivers/pci/search.c  |  6 ++++++
> >  include/linux/pci.h   |  1 +
> >  4 files changed, 35 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
> > index 1e59df0..fe21a5c 100644
> > --- a/arch/x86/pci/common.c
> > +++ b/arch/x86/pci/common.c
> > @@ -736,3 +736,13 @@ int pci_ext_cfg_avail(void)
> >  	else
> >  		return 0;
> >  }
> > +
> > +#if IS_ENABLED(CONFIG_VMD)
> > +struct pci_dev *pci_real_dma_dev(struct pci_dev *dev)
> > +{
> > +	if (is_vmd(dev->bus))
> > +		return to_pci_sysdata(dev->bus)->vmd_dev;
> > +
> > +	return dev;
> > +}
> > +#endif
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index 581b177..36d24f2 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -6048,7 +6048,9 @@ bool pci_devs_are_dma_aliases(struct pci_dev *dev1, struct pci_dev *dev2)
> >  	return (dev1->dma_alias_mask &&
> >  		test_bit(dev2->devfn, dev1->dma_alias_mask)) ||
> >  	       (dev2->dma_alias_mask &&
> > -		test_bit(dev1->devfn, dev2->dma_alias_mask));
> > +		test_bit(dev1->devfn, dev2->dma_alias_mask)) ||
> > +	       pci_real_dma_dev(dev1) == dev2 ||
> > +	       pci_real_dma_dev(dev2) == dev1;
> >  }
> >  
> >  bool pci_device_is_present(struct pci_dev *pdev)
> > @@ -6072,6 +6074,21 @@ void pci_ignore_hotplug(struct pci_dev *dev)
> >  }
> >  EXPORT_SYMBOL_GPL(pci_ignore_hotplug);
> >  
> > +/**
> > + * pci_real_dma_dev - Get PCI DMA device for PCI device
> > + * @dev: the PCI device that may have a PCI DMA alias
> > + *
> > + * Permits the platform to provide architecture-specific functionality to
> > + * devices needing to alias DMA to another PCI device on another PCI bus. If
> > + * the PCI device is on the same bus, it is recommended to use
> > + * pci_add_dma_alias(). This is the default implementation. Architecture
> > + * implementations can override this.
> > + */
> > +struct pci_dev __weak *pci_real_dma_dev(struct pci_dev *dev)
> > +{
> > +	return dev;
> > +}
> > +
> >  resource_size_t __weak pcibios_default_alignment(void)
> >  {
> >  	return 0;
> > diff --git a/drivers/pci/search.c b/drivers/pci/search.c
> > index e4dbdef..2061672 100644
> > --- a/drivers/pci/search.c
> > +++ b/drivers/pci/search.c
> > @@ -32,6 +32,12 @@ int pci_for_each_dma_alias(struct pci_dev *pdev,
> >  	struct pci_bus *bus;
> >  	int ret;
> >  
> > +	/*
> > +	 * The device may have an explicit alias requester ID for DMA where the
> > +	 * requester is on another PCI bus.
> > +	 */
> > +	pdev = pci_real_dma_dev(pdev);
> >  	ret = fn(pdev, pci_dev_id(pdev), data);
> >  	if (ret)
> >  		return ret;
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index 930fab2..3840a54 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -1202,6 +1202,7 @@ u32 pcie_bandwidth_available(struct pci_dev *dev, struct pci_dev **limiting_dev,
> >  int pci_select_bars(struct pci_dev *dev, unsigned long flags);
> >  bool pci_device_is_present(struct pci_dev *pdev);
> >  void pci_ignore_hotplug(struct pci_dev *dev);
> > +struct pci_dev *pci_real_dma_dev(struct pci_dev *dev);
> >  
> >  int __printf(6, 7) pci_request_irq(struct pci_dev *dev, unsigned int nr,
> >  		irq_handler_t handler, irq_handler_t thread_fn, void *dev_id,
> > -- 
> > 1.8.3.1
> >