From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.136]:59911 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751221AbcA0AEH (ORCPT ); Tue, 26 Jan 2016 19:04:07 -0500 Date: Tue, 26 Jan 2016 18:04:03 -0600 From: Bjorn Helgaas To: Alex Williamson Cc: Jacek Lawrynowicz , linux-pci@vger.kernel.org, bhelgaas@google.com, dwmw2@infradead.org, jroedel@suse.de Subject: Re: [PATCH v2 1/2] pci: Add support for multiple DMA aliases Message-ID: <20160127000403.GA3102@localhost> References: <1453825639.26652.45.camel@redhat.com> <1453828335-111522-1-git-send-email-jacek.lawrynowicz@intel.com> <20160126233100.GC26726@localhost> <1453851743.21982.1.camel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <1453851743.21982.1.camel@redhat.com> Sender: linux-pci-owner@vger.kernel.org List-ID: On Tue, Jan 26, 2016 at 04:42:23PM -0700, Alex Williamson wrote: > On Tue, 2016-01-26 at 17:31 -0600, Bjorn Helgaas wrote: > > Hi Jacek, > >  > > When you post updated versions, please post the whole series with a > > new version number.  I think there are three postings of [v2 1/2], and > > I think they're different.  In any case, it's hard for me to keep them > > straight. > >  > > On Tue, Jan 26, 2016 at 06:12:15PM +0100, Jacek Lawrynowicz wrote: > > > This patch solves IOMMU support issues with PCIe non-transparent bridges > > > that use Requester ID look-up tables (LUT), e.g. PEX8733. Before exiting > > > the bridge, packet's RID is rewritten according to LUT programmed by > > > a driver. Modified packets are then passed to a destination bus and > > > processed upstream. The problem is that such packets seem to come from > > > non-existent nodes that are hidden behind NTB and are not discoverable > > > by a destination node, so IOMMU discards them. Adding DMA alias for a > > > given LUT entry allows IOMMU to create a proper mapping that enables > > > inter-node communication. > > >  > > > The current DMA alias implementation supports only single alias, so it's > > > not possible to connect more than two nodes when IOMMU is enabled. This > > > implementation enables all possible aliases on a given bus (256) that > > > are stored in a bitset. Alias devfn is directly translated to a bit > > > number. The bitset is not allocated for devices that have no need for > > > DMA aliases. > > >  > > > More details can be found in following article: > > > http://www.plxtech.com/files/pdf/technical/expresslane/RTC_Enabling%20MulitHostSystemDesigns.pdf > > >  > > > Signed-off-by: Jacek Lawrynowicz > > > Acked-By: David Woodhouse > > > --- > > >  drivers/iommu/iommu.c | 11 ++++------- > > >  drivers/pci/pci.c     | 27 +++++++++++++++++++++++++++ > > >  drivers/pci/pci.h     |  2 ++ > > >  drivers/pci/probe.c   |  1 + > > >  drivers/pci/quirks.c  | 15 ++++++--------- > > >  drivers/pci/search.c  | 14 +++++++++----- > > >  include/linux/pci.h   | 14 +++++++------- > > >  7 files changed, 56 insertions(+), 28 deletions(-) > > >  > > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > > > index 0e3b009..93a89ed 100644 > > > --- a/drivers/iommu/iommu.c > > > +++ b/drivers/iommu/iommu.c > > > @@ -660,8 +660,8 @@ static struct iommu_group *get_pci_function_alias_group(struct pci_dev > > > *pdev, > > >  } > > >   > > >  /* > > > - * Look for aliases to or from the given device for exisiting groups.  The > > > - * dma_alias_devfn only supports aliases on the same bus, therefore the search > > > + * Look for aliases to or from the given device for exisiting groups. DMA > >  > > s/exisiting/existing/  (Not your change, but might as well fix the > > typo since you're touching the line anyway.) > >  > > > + * aliases are only supported on the same bus, therefore the search > > >   * space is quite small (especially since we're really only looking at pcie > > >   * device, and therefore only expect multiple slots on the root complex or > > >   * downstream switch ports).  It's conceivable though that a pair of > > > @@ -686,11 +686,8 @@ static struct iommu_group *get_pci_alias_group(struct pci_dev *pdev, > > >   continue; > > >   > > >   /* We alias them or they alias us */ > > > - if (((pdev->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_DEVFN) && > > > -      pdev->dma_alias_devfn == tmp->devfn) || > > > -     ((tmp->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_DEVFN) && > > > -      tmp->dma_alias_devfn == pdev->devfn)) { > > > - > > > + if (pci_dma_alias_is_enabled(pdev, tmp->devfn) || > > > +     pci_dma_alias_is_enabled(tmp, pdev->devfn)) { > >  > > I was hoping for something that took two pci_dev pointers and returned > > true if they were aliases of each other, e.g., > >  > >   bool pci_dma_aliases(struct pci_dev *dev1, struct pci_dev *dev2); > > Such a thing could already be created with pci_for_each_dma_alias(). Does that mean we could get replace the use of for_each_pci_dev() with some clever use of pci_for_each_dma_alias()?