| Message ID | 1462700001-30086-1-git-send-email-jchandra@broadcom.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On 08/05/16 10:33, Jayachandran C via iommu wrote: > Add a new flag PCI_DEV_FLAGS_DMA_ALIAS_ROOT to limit the DMA alias > search to go no further than the bridge where the IOMMU is attached. > > This has been added to support Broadcom's Vulcan which has the SMMUv3 > and GIC ITS associated with an intermediate bridge in the PCI topology. > Traversing to buses above would hit internal glue bridges which will > change the RID. Can you not just have the relevant callback function detect the relevant node and terminate the walk of its own accord? That's what I was aiming for in this patch for the IOMMU setup: http://article.gmane.org/gmane.linux.kernel.iommu/12456 Is there some flaw in that approach I've missed? Robin. > Update the function pci_for_each_dma_alias() to stop when it see a > bridge with this flag set. > > Signed-off-by: Jayachandran C <jchandra@broadcom.com> > --- > > Here is v2 of the patch, the previous discussion is at > http://lists.linuxfoundation.org/pipermail/iommu/2016-February/015668.html > > v1->v2 changes: > - dropped the BAR quirk (not needed) > - moved from using the 'skip' flag for some bridges to using > similar approach to stop the traversal at the bridge with > PCI_DEV_FLAGS_DMA_ALIAS_ROOT > > Comments and suggestions are welcome > > JC. > > drivers/pci/search.c | 4 ++++ > include/linux/pci.h | 2 ++ > 2 files changed, 6 insertions(+) > > diff --git a/drivers/pci/search.c b/drivers/pci/search.c > index a20ce7d..3ea9c27 100644 > --- a/drivers/pci/search.c > +++ b/drivers/pci/search.c > @@ -56,6 +56,10 @@ int pci_for_each_dma_alias(struct pci_dev *pdev, > > tmp = bus->self; > > + /* stop at bridge where translation unit is associated */ > + if (tmp->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_ROOT) > + return ret; > + > /* > * PCIe-to-PCI/X bridges alias transactions from downstream > * devices using the subordinate bus number (PCI Express to > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 932ec74..b6f832b 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -176,6 +176,8 @@ enum pci_dev_flags { > PCI_DEV_FLAGS_NO_PM_RESET = (__force pci_dev_flags_t) (1 << 7), > /* Get VPD from function 0 VPD */ > PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 8), > + /* a non-root bridge where translation occurs, stop alias search here */ > + PCI_DEV_FLAGS_DMA_ALIAS_ROOT = (__force pci_dev_flags_t) (1 << 9), > }; > > enum pci_irq_reroute_variant { > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, May 9, 2016 at 3:40 PM, Robin Murphy <robin.murphy@arm.com> wrote: > On 08/05/16 10:33, Jayachandran C via iommu wrote: >> >> Add a new flag PCI_DEV_FLAGS_DMA_ALIAS_ROOT to limit the DMA alias >> search to go no further than the bridge where the IOMMU is attached. >> >> This has been added to support Broadcom's Vulcan which has the SMMUv3 >> and GIC ITS associated with an intermediate bridge in the PCI topology. >> Traversing to buses above would hit internal glue bridges which will >> change the RID. > > > Can you not just have the relevant callback function detect the relevant > node and terminate the walk of its own accord? That's what I was aiming for > in this patch for the IOMMU setup: > > http://article.gmane.org/gmane.linux.kernel.iommu/12456 > > Is there some flaw in that approach I've missed? Not flaw as such, but: - We need to support OF as well as ACPI, so the firmware dependent approach will not work. The ACPI code does not exist right now, but there are patches for this in development. - GICv3 ITS also uses the RIDs. I need to replicate the same logic in pci/msi.c and irqchip/irq-gic-v3-its-pci-msi.c for MSI. For IOMMU, I have to update iommu/arm-smmu-v3.c and in other places in iommu code where pci_for_each_dma_alias is called. - since it is non-standard PCIe topology for the processor, a quirk seemed to be the right way to handle it. I am still figuring out the right approach here, so comments are welcome. JC. > >> Update the function pci_for_each_dma_alias() to stop when it see a >> bridge with this flag set. >> >> Signed-off-by: Jayachandran C <jchandra@broadcom.com> >> --- >> >> Here is v2 of the patch, the previous discussion is at >> http://lists.linuxfoundation.org/pipermail/iommu/2016-February/015668.html >> >> v1->v2 changes: >> - dropped the BAR quirk (not needed) >> - moved from using the 'skip' flag for some bridges to using >> similar approach to stop the traversal at the bridge with >> PCI_DEV_FLAGS_DMA_ALIAS_ROOT >> >> Comments and suggestions are welcome >> >> JC. >> >> drivers/pci/search.c | 4 ++++ >> include/linux/pci.h | 2 ++ >> 2 files changed, 6 insertions(+) >> >> diff --git a/drivers/pci/search.c b/drivers/pci/search.c >> index a20ce7d..3ea9c27 100644 >> --- a/drivers/pci/search.c >> +++ b/drivers/pci/search.c >> @@ -56,6 +56,10 @@ int pci_for_each_dma_alias(struct pci_dev *pdev, >> >> tmp = bus->self; >> >> + /* stop at bridge where translation unit is associated */ >> + if (tmp->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_ROOT) >> + return ret; >> + >> /* >> * PCIe-to-PCI/X bridges alias transactions from >> downstream >> * devices using the subordinate bus number (PCI Express >> to >> diff --git a/include/linux/pci.h b/include/linux/pci.h >> index 932ec74..b6f832b 100644 >> --- a/include/linux/pci.h >> +++ b/include/linux/pci.h >> @@ -176,6 +176,8 @@ enum pci_dev_flags { >> PCI_DEV_FLAGS_NO_PM_RESET = (__force pci_dev_flags_t) (1 << 7), >> /* Get VPD from function 0 VPD */ >> PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 8), >> + /* a non-root bridge where translation occurs, stop alias search >> here */ >> + PCI_DEV_FLAGS_DMA_ALIAS_ROOT = (__force pci_dev_flags_t) (1 << 9), >> }; >> >> enum pci_irq_reroute_variant { >> > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 11/05/16 07:28, Jayachandran C wrote: > On Mon, May 9, 2016 at 3:40 PM, Robin Murphy <robin.murphy@arm.com> wrote: >> On 08/05/16 10:33, Jayachandran C via iommu wrote: >>> >>> Add a new flag PCI_DEV_FLAGS_DMA_ALIAS_ROOT to limit the DMA alias >>> search to go no further than the bridge where the IOMMU is attached. >>> >>> This has been added to support Broadcom's Vulcan which has the SMMUv3 >>> and GIC ITS associated with an intermediate bridge in the PCI topology. >>> Traversing to buses above would hit internal glue bridges which will >>> change the RID. >> >> >> Can you not just have the relevant callback function detect the relevant >> node and terminate the walk of its own accord? That's what I was aiming for >> in this patch for the IOMMU setup: >> >> http://article.gmane.org/gmane.linux.kernel.iommu/12456 >> >> Is there some flaw in that approach I've missed? > > Not flaw as such, but: > - We need to support OF as well as ACPI, so the firmware dependent > approach will not work. The ACPI code does not exist right now, but > there are patches for this in development. > - GICv3 ITS also uses the RIDs. I need to replicate the same logic in > pci/msi.c and irqchip/irq-gic-v3-its-pci-msi.c for MSI. For IOMMU, I > have to update iommu/arm-smmu-v3.c and in other places in iommu > code where pci_for_each_dma_alias is called. > - since it is non-standard PCIe topology for the processor, a quirk seemed > to be the right way to handle it. > > I am still figuring out the right approach here, so comments are welcome. Oh for sure, I didn't mean to imply that that code is a complete ready-made solution, just that in general it seems a fairly straightforward thing to handle without touching the PCI core: - We already have to know whichever parent device has the msi-map/iommu-map/IORT table. - We're aware of that parent at the point we're doing the DMA/MSI configuration. - Therefore those operations already have everything they need for their callback to be able to stop when it reaches the relevant parent device. Doing it in a firmware-agnostic manner is merely an implementation detail. Since we'll basically be funnelling both MSI and IOMMU RID translation through a common code path, there should only need to be be one place to handle the DMA alias walk - with that first cut of my PCI/generic IOMMU bindings series I didn't try very hard to refactor things - v2 (probably post-merge-window now) will be a bit more thorough, now that I have a better idea of what thing should look like Ignore what arm-smmu-v3.c does, because it's wrong anyway. I need to fix that in the next version as well, even if it's just calling out directly to of_pci_map_rid rather than a proper of_xlate implementation. Now what I realise I *have* missed is the alias detection in iommu_get_group_for_dev, to which the "known parent device" reasoning doesn't apply, and phantom aliasing might well muck things up. Thinking further, if these upstream bridges exist but don't affect the outgoing RID, then might it make sense to quirk them as transparent? (I have no actual objection to this patch, though, and at this point I'm just chucking ideas about). Robin. > JC. > >> >>> Update the function pci_for_each_dma_alias() to stop when it see a >>> bridge with this flag set. >>> >>> Signed-off-by: Jayachandran C <jchandra@broadcom.com> >>> --- >>> >>> Here is v2 of the patch, the previous discussion is at >>> http://lists.linuxfoundation.org/pipermail/iommu/2016-February/015668.html >>> >>> v1->v2 changes: >>> - dropped the BAR quirk (not needed) >>> - moved from using the 'skip' flag for some bridges to using >>> similar approach to stop the traversal at the bridge with >>> PCI_DEV_FLAGS_DMA_ALIAS_ROOT >>> >>> Comments and suggestions are welcome >>> >>> JC. >>> >>> drivers/pci/search.c | 4 ++++ >>> include/linux/pci.h | 2 ++ >>> 2 files changed, 6 insertions(+) >>> >>> diff --git a/drivers/pci/search.c b/drivers/pci/search.c >>> index a20ce7d..3ea9c27 100644 >>> --- a/drivers/pci/search.c >>> +++ b/drivers/pci/search.c >>> @@ -56,6 +56,10 @@ int pci_for_each_dma_alias(struct pci_dev *pdev, >>> >>> tmp = bus->self; >>> >>> + /* stop at bridge where translation unit is associated */ >>> + if (tmp->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_ROOT) >>> + return ret; >>> + >>> /* >>> * PCIe-to-PCI/X bridges alias transactions from >>> downstream >>> * devices using the subordinate bus number (PCI Express >>> to >>> diff --git a/include/linux/pci.h b/include/linux/pci.h >>> index 932ec74..b6f832b 100644 >>> --- a/include/linux/pci.h >>> +++ b/include/linux/pci.h >>> @@ -176,6 +176,8 @@ enum pci_dev_flags { >>> PCI_DEV_FLAGS_NO_PM_RESET = (__force pci_dev_flags_t) (1 << 7), >>> /* Get VPD from function 0 VPD */ >>> PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 8), >>> + /* a non-root bridge where translation occurs, stop alias search >>> here */ >>> + PCI_DEV_FLAGS_DMA_ALIAS_ROOT = (__force pci_dev_flags_t) (1 << 9), >>> }; >>> >>> enum pci_irq_reroute_variant { >>> >> > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, May 11, 2016 at 7:56 PM, Robin Murphy <robin.murphy@arm.com> wrote: > On 11/05/16 07:28, Jayachandran C wrote: >> >> On Mon, May 9, 2016 at 3:40 PM, Robin Murphy <robin.murphy@arm.com> wrote: >>> >>> On 08/05/16 10:33, Jayachandran C via iommu wrote: >>>> >>>> >>>> Add a new flag PCI_DEV_FLAGS_DMA_ALIAS_ROOT to limit the DMA alias >>>> search to go no further than the bridge where the IOMMU is attached. >>>> >>>> This has been added to support Broadcom's Vulcan which has the SMMUv3 >>>> and GIC ITS associated with an intermediate bridge in the PCI topology. >>>> Traversing to buses above would hit internal glue bridges which will >>>> change the RID. >>> >>> >>> >>> Can you not just have the relevant callback function detect the relevant >>> node and terminate the walk of its own accord? That's what I was aiming >>> for >>> in this patch for the IOMMU setup: >>> >>> http://article.gmane.org/gmane.linux.kernel.iommu/12456 >>> >>> Is there some flaw in that approach I've missed? >> >> >> Not flaw as such, but: >> - We need to support OF as well as ACPI, so the firmware dependent >> approach will not work. The ACPI code does not exist right now, but >> there are patches for this in development. >> - GICv3 ITS also uses the RIDs. I need to replicate the same logic in >> pci/msi.c and irqchip/irq-gic-v3-its-pci-msi.c for MSI. For IOMMU, I >> have to update iommu/arm-smmu-v3.c and in other places in iommu >> code where pci_for_each_dma_alias is called. >> - since it is non-standard PCIe topology for the processor, a quirk >> seemed >> to be the right way to handle it. >> >> I am still figuring out the right approach here, so comments are welcome. > > > Oh for sure, I didn't mean to imply that that code is a complete ready-made > solution, just that in general it seems a fairly straightforward thing to > handle without touching the PCI core: > > - We already have to know whichever parent device has the > msi-map/iommu-map/IORT table. > - We're aware of that parent at the point we're doing the DMA/MSI > configuration. > - Therefore those operations already have everything they need for their > callback to be able to stop when it reaches the relevant parent device. > Doing it in a firmware-agnostic manner is merely an implementation detail. > > Since we'll basically be funnelling both MSI and IOMMU RID translation > through a common code path, there should only need to be be one place to > handle the DMA alias walk - with that first cut of my PCI/generic IOMMU > bindings series I didn't try very hard to refactor things - v2 (probably > post-merge-window now) will be a bit more thorough, now that I have a better > idea of what thing should look like > > Ignore what arm-smmu-v3.c does, because it's wrong anyway. I need to fix > that in the next version as well, even if it's just calling out directly to > of_pci_map_rid rather than a proper of_xlate implementation. > > Now what I realise I *have* missed is the alias detection in > iommu_get_group_for_dev, to which the "known parent device" reasoning > doesn't apply, and phantom aliasing might well muck things up. Thinking > further, if these upstream bridges exist but don't affect the outgoing RID, > then might it make sense to quirk them as transparent? (I have no actual > objection to this patch, though, and at this point I'm just chucking ideas > about). I had an earlier patch that had a quirk which marked some bridges to be skipped https://patchwork.ozlabs.org/patch/582633/ which is similar to the transparent idea. The discussion on that patch seems to indicate that having a "root" flag may be better. > Robin. [...] JC. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 05/11/2016 10:26 AM, Robin Murphy wrote: > (I have no actual objection to this patch, though, and at this point > I'm just chucking ideas about). Can I ask what the next steps are here? We're looking for upstream direction to guide some internal activities and could really do with understanding how you'd like to solve this one longer term as well as what interim solution could be acceptable until we get there. Jon.
On 23/06/16 06:01, Jon Masters wrote: > On 05/11/2016 10:26 AM, Robin Murphy wrote: >> (I have no actual objection to this patch, though, and at this point >> I'm just chucking ideas about). > > Can I ask what the next steps are here? We're looking for upstream > direction to guide some internal activities and could really do with > understanding how you'd like to solve this one longer term as well as > what interim solution could be acceptable until we get there. Well, for now I'm planning to leave the explicit "terminate the alias walk from the callback function" behaviour in the DT-parsing code[1], since there doesn't seem any good reason not to. As Bjorn says, though, it probably is generally useful for the PCI code to have its own knowledge of exactly where DMA can escape the PCI hierarchy - I now wonder if we could actually just do that from the DT/IORT code; if firmware says a particular bridge/etc. has a relationship with an ITS or SMMU, then presumably it's reasonable to infer that DMA can come out of it, thus we could inform the PCI code there and then without it having to quirk things on its own? Robin. [1]:http://article.gmane.org/gmane.linux.kernel.iommu/13932 > > Jon. > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Quick reply (sorry about top post): I am just getting online so I might discover that this callback is shared by both - in which case, cool - but if not, we need an interim ACPI solution. Aside: Current RHEL Server for ARM (RHELSA) explicitly disables SMMUv3 support because (I warned the folks involved more than a year ago), we will only support ACPI/IORT, and as you can imagine, many people would like us to enable support for device passthrough and robustness, not to mention 32-bit devices (32-bit DMA mask). Nonetheless, that will only happen when the upstream kernel has IORT and quirks in place.
On Thu, Jun 23, 2016 at 01:04:01PM +0100, Robin Murphy wrote: > On 23/06/16 06:01, Jon Masters wrote: > >On 05/11/2016 10:26 AM, Robin Murphy wrote: > >>(I have no actual objection to this patch, though, and at this point > >>I'm just chucking ideas about). > > > >Can I ask what the next steps are here? We're looking for upstream > >direction to guide some internal activities and could really do with > >understanding how you'd like to solve this one longer term as well as > >what interim solution could be acceptable until we get there. > > Well, for now I'm planning to leave the explicit "terminate the > alias walk from the callback function" behaviour in the DT-parsing > code[1], since there doesn't seem any good reason not to. As Bjorn > says, though, it probably is generally useful for the PCI code to > have its own knowledge of exactly where DMA can escape the PCI > hierarchy - I now wonder if we could actually just do that from the > DT/IORT code; if firmware says a particular bridge/etc. has a > relationship with an ITS or SMMU, then presumably it's reasonable to > infer that DMA can come out of it, thus we could inform the PCI code > there and then without it having to quirk things on its own? > > Robin. > > [1]:http://article.gmane.org/gmane.linux.kernel.iommu/13932 Just a reminder that I'm going to be on vacation for about the next three weeks, so it's not that I'm ignoring this, but it seems like it's not fully baked quite yet. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/pci/search.c b/drivers/pci/search.c index a20ce7d..3ea9c27 100644 --- a/drivers/pci/search.c +++ b/drivers/pci/search.c @@ -56,6 +56,10 @@ int pci_for_each_dma_alias(struct pci_dev *pdev, tmp = bus->self; + /* stop at bridge where translation unit is associated */ + if (tmp->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_ROOT) + return ret; + /* * PCIe-to-PCI/X bridges alias transactions from downstream * devices using the subordinate bus number (PCI Express to diff --git a/include/linux/pci.h b/include/linux/pci.h index 932ec74..b6f832b 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -176,6 +176,8 @@ enum pci_dev_flags { PCI_DEV_FLAGS_NO_PM_RESET = (__force pci_dev_flags_t) (1 << 7), /* Get VPD from function 0 VPD */ PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 8), + /* a non-root bridge where translation occurs, stop alias search here */ + PCI_DEV_FLAGS_DMA_ALIAS_ROOT = (__force pci_dev_flags_t) (1 << 9), }; enum pci_irq_reroute_variant {
Add a new flag PCI_DEV_FLAGS_DMA_ALIAS_ROOT to limit the DMA alias search to go no further than the bridge where the IOMMU is attached. This has been added to support Broadcom's Vulcan which has the SMMUv3 and GIC ITS associated with an intermediate bridge in the PCI topology. Traversing to buses above would hit internal glue bridges which will change the RID. Update the function pci_for_each_dma_alias() to stop when it see a bridge with this flag set. Signed-off-by: Jayachandran C <jchandra@broadcom.com> --- Here is v2 of the patch, the previous discussion is at http://lists.linuxfoundation.org/pipermail/iommu/2016-February/015668.html v1->v2 changes: - dropped the BAR quirk (not needed) - moved from using the 'skip' flag for some bridges to using similar approach to stop the traversal at the bridge with PCI_DEV_FLAGS_DMA_ALIAS_ROOT Comments and suggestions are welcome JC. drivers/pci/search.c | 4 ++++ include/linux/pci.h | 2 ++ 2 files changed, 6 insertions(+)