* [PATCH] pci: Fix flaw in pci_acs_enabled() @ 2013-05-30 18:37 Alex Williamson 2013-05-30 19:35 ` Don Dutile 0 siblings, 1 reply; 3+ messages in thread From: Alex Williamson @ 2013-05-30 18:37 UTC (permalink / raw) To: bhelgaas, linux-pci; +Cc: ddutile, linux-kernel Downstream ports support for all ACS flags supercedes multifunction exclusion of some flags. The PCIe spec also fully specifies which PCIe types are subject to the multifunction rules and excludes event collectors and PCIe-to-PCI bridges entirely. Document each rule to the section of the PCIe spec. Signed-off-by: Alex Williamson <alex.williamson@redhat.com> --- drivers/pci/pci.c | 59 ++++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 45 insertions(+), 14 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index b099e00..457ae51 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -2354,6 +2354,19 @@ void pci_enable_acs(struct pci_dev *dev) pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl); } +static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags) +{ + int pos; + u16 ctrl; + + pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS); + if (!pos) + return false; + + pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl); + return (ctrl & acs_flags) == acs_flags; +} + /** * pci_acs_enabled - test ACS against required flags for a given device * @pdev: device to test @@ -2364,8 +2377,7 @@ void pci_enable_acs(struct pci_dev *dev) */ bool pci_acs_enabled(struct pci_dev *pdev, u16 acs_flags) { - int pos, ret; - u16 ctrl; + int ret; ret = pci_dev_specific_acs_enabled(pdev, acs_flags); if (ret >= 0) @@ -2374,23 +2386,42 @@ bool pci_acs_enabled(struct pci_dev *pdev, u16 acs_flags) if (!pci_is_pcie(pdev)) return false; - /* Filter out flags not applicable to multifunction */ - if (pdev->multifunction) + switch (pci_pcie_type(pdev)) { + /* + * PCIe 3.0, 6.12.1 excludes ACS on these devices. "Not applicable" + */ + case PCI_EXP_TYPE_PCI_BRIDGE: + case PCI_EXP_TYPE_RC_EC: + break; + /* + * PCIe 3.0, 6.12.1.1 specifies full ACS capabilities on downstream + * ports, regardless of them being multifunction devices. + */ + case PCI_EXP_TYPE_DOWNSTREAM: + case PCI_EXP_TYPE_ROOT_PORT: + return pci_acs_flags_enabled(pdev, acs_flags); + /* + * PCIe 3.0, 6.12.1.2 specifies unimplemented ACS capabilities on + * multifunction devices. 6.12 footnote identifies specifically + * which devices types this applies to. + */ + case PCI_EXP_TYPE_ENDPOINT: + case PCI_EXP_TYPE_UPSTREAM: + case PCI_EXP_TYPE_LEG_END: + case PCI_EXP_TYPE_RC_END: + if (!pdev->multifunction) + break; + acs_flags &= (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC | PCI_ACS_DT); - if (pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM || - pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT || - pdev->multifunction) { - pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS); - if (!pos) - return false; - - pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl); - if ((ctrl & acs_flags) != acs_flags) - return false; + return pci_acs_flags_enabled(pdev, acs_flags); } + /* + * PCIe 3.0, 6.12.1.3 specifies no ACS capabilties are applicable + * to single function devices with the exception of downstream ports. + */ return true; } ^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] pci: Fix flaw in pci_acs_enabled() 2013-05-30 18:37 [PATCH] pci: Fix flaw in pci_acs_enabled() Alex Williamson @ 2013-05-30 19:35 ` Don Dutile 2013-05-30 19:55 ` Alex Williamson 0 siblings, 1 reply; 3+ messages in thread From: Don Dutile @ 2013-05-30 19:35 UTC (permalink / raw) To: Alex Williamson; +Cc: bhelgaas, linux-pci, linux-kernel On 05/30/2013 02:37 PM, Alex Williamson wrote: > Downstream ports support for all ACS flags supercedes multifunction > exclusion of some flags. The PCIe spec also fully specifies which > PCIe types are subject to the multifunction rules and excludes event > collectors and PCIe-to-PCI bridges entirely. Document each rule to > the section of the PCIe spec. > > Signed-off-by: Alex Williamson<alex.williamson@redhat.com> > --- > drivers/pci/pci.c | 59 ++++++++++++++++++++++++++++++++++++++++------------- > 1 file changed, 45 insertions(+), 14 deletions(-) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index b099e00..457ae51 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -2354,6 +2354,19 @@ void pci_enable_acs(struct pci_dev *dev) > pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl); > } > > +static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags) > +{ > + int pos; > + u16 ctrl; > + > + pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS); > + if (!pos) > + return false; > + > + pci_read_config_word(pdev, pos + PCI_ACS_CTRL,&ctrl); > + return (ctrl& acs_flags) == acs_flags; > +} > + > /** > * pci_acs_enabled - test ACS against required flags for a given device > * @pdev: device to test > @@ -2364,8 +2377,7 @@ void pci_enable_acs(struct pci_dev *dev) > */ > bool pci_acs_enabled(struct pci_dev *pdev, u16 acs_flags) > { > - int pos, ret; > - u16 ctrl; > + int ret; > > ret = pci_dev_specific_acs_enabled(pdev, acs_flags); > if (ret>= 0) > @@ -2374,23 +2386,42 @@ bool pci_acs_enabled(struct pci_dev *pdev, u16 acs_flags) > if (!pci_is_pcie(pdev)) > return false; > > - /* Filter out flags not applicable to multifunction */ > - if (pdev->multifunction) > + switch (pci_pcie_type(pdev)) { > + /* > + * PCIe 3.0, 6.12.1 excludes ACS on these devices. "Not applicable" > + */ > + case PCI_EXP_TYPE_PCI_BRIDGE: > + case PCI_EXP_TYPE_RC_EC: > + break; > + /* > + * PCIe 3.0, 6.12.1.1 specifies full ACS capabilities on downstream > + * ports, regardless of them being multifunction devices. > + */ > + case PCI_EXP_TYPE_DOWNSTREAM: > + case PCI_EXP_TYPE_ROOT_PORT: > + return pci_acs_flags_enabled(pdev, acs_flags); > + /* > + * PCIe 3.0, 6.12.1.2 specifies unimplemented ACS capabilities on > + * multifunction devices. 6.12 footnote identifies specifically > + * which devices types this applies to. > + */ > + case PCI_EXP_TYPE_ENDPOINT: > + case PCI_EXP_TYPE_UPSTREAM: > + case PCI_EXP_TYPE_LEG_END: > + case PCI_EXP_TYPE_RC_END: > + if (!pdev->multifunction) > + break; > + > acs_flags&= (PCI_ACS_RR | PCI_ACS_CR | > PCI_ACS_EC | PCI_ACS_DT); > > - if (pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM || > - pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT || > - pdev->multifunction) { > - pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS); > - if (!pos) > - return false; > - > - pci_read_config_word(pdev, pos + PCI_ACS_CTRL,&ctrl); > - if ((ctrl& acs_flags) != acs_flags) > - return false; > + return pci_acs_flags_enabled(pdev, acs_flags); As I read 6.12.1.2, *if* a multifunction device supports peer-to-peer traffic with another function(s), then certain ACS subfunctions must be implemented. So, I conclude from that statement (3rd bullet under this section), if a MFD does not support peer-to-peer traffic, it doesn't have to provide an ACS cap ... which is what I'm seeing in a number of MFD NICs (with sriov devices). IOW, an MFD w/o an ACS cap == single function device w/o ACS cap. If that spec interpretation, and more importantly, hw implementation, is correct, then won't above code return 'false' for an MFD with no ACS cap, and shouldn't it return true in that case b/c it's optional/only-req'd if MFD has peer-to-peer btwn functions? > } > > + /* > + * PCIe 3.0, 6.12.1.3 specifies no ACS capabilties are applicable > + * to single function devices with the exception of downstream ports. > + */ > return true; > } > > > -- > 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 ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] pci: Fix flaw in pci_acs_enabled() 2013-05-30 19:35 ` Don Dutile @ 2013-05-30 19:55 ` Alex Williamson 0 siblings, 0 replies; 3+ messages in thread From: Alex Williamson @ 2013-05-30 19:55 UTC (permalink / raw) To: Don Dutile; +Cc: bhelgaas, linux-pci, linux-kernel On Thu, 2013-05-30 at 15:35 -0400, Don Dutile wrote: > On 05/30/2013 02:37 PM, Alex Williamson wrote: > > Downstream ports support for all ACS flags supercedes multifunction > > exclusion of some flags. The PCIe spec also fully specifies which > > PCIe types are subject to the multifunction rules and excludes event > > collectors and PCIe-to-PCI bridges entirely. Document each rule to > > the section of the PCIe spec. > > > > Signed-off-by: Alex Williamson<alex.williamson@redhat.com> > > --- > > drivers/pci/pci.c | 59 ++++++++++++++++++++++++++++++++++++++++------------- > > 1 file changed, 45 insertions(+), 14 deletions(-) > > > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > > index b099e00..457ae51 100644 > > --- a/drivers/pci/pci.c > > +++ b/drivers/pci/pci.c > > @@ -2354,6 +2354,19 @@ void pci_enable_acs(struct pci_dev *dev) > > pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl); > > } > > > > +static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags) > > +{ > > + int pos; > > + u16 ctrl; > > + > > + pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS); > > + if (!pos) > > + return false; > > + > > + pci_read_config_word(pdev, pos + PCI_ACS_CTRL,&ctrl); > > + return (ctrl& acs_flags) == acs_flags; > > +} > > + > > /** > > * pci_acs_enabled - test ACS against required flags for a given device > > * @pdev: device to test > > @@ -2364,8 +2377,7 @@ void pci_enable_acs(struct pci_dev *dev) > > */ > > bool pci_acs_enabled(struct pci_dev *pdev, u16 acs_flags) > > { > > - int pos, ret; > > - u16 ctrl; > > + int ret; > > > > ret = pci_dev_specific_acs_enabled(pdev, acs_flags); > > if (ret>= 0) > > @@ -2374,23 +2386,42 @@ bool pci_acs_enabled(struct pci_dev *pdev, u16 acs_flags) > > if (!pci_is_pcie(pdev)) > > return false; > > > > - /* Filter out flags not applicable to multifunction */ > > - if (pdev->multifunction) > > + switch (pci_pcie_type(pdev)) { > > + /* > > + * PCIe 3.0, 6.12.1 excludes ACS on these devices. "Not applicable" > > + */ > > + case PCI_EXP_TYPE_PCI_BRIDGE: > > + case PCI_EXP_TYPE_RC_EC: > > + break; > > + /* > > + * PCIe 3.0, 6.12.1.1 specifies full ACS capabilities on downstream > > + * ports, regardless of them being multifunction devices. > > + */ > > + case PCI_EXP_TYPE_DOWNSTREAM: > > + case PCI_EXP_TYPE_ROOT_PORT: > > + return pci_acs_flags_enabled(pdev, acs_flags); > > + /* > > + * PCIe 3.0, 6.12.1.2 specifies unimplemented ACS capabilities on > > + * multifunction devices. 6.12 footnote identifies specifically > > + * which devices types this applies to. > > + */ > > + case PCI_EXP_TYPE_ENDPOINT: > > + case PCI_EXP_TYPE_UPSTREAM: > > + case PCI_EXP_TYPE_LEG_END: > > + case PCI_EXP_TYPE_RC_END: > > + if (!pdev->multifunction) > > + break; > > + > > > > acs_flags&= (PCI_ACS_RR | PCI_ACS_CR | > > PCI_ACS_EC | PCI_ACS_DT); > > > > - if (pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM || > > - pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT || > > - pdev->multifunction) { > > - pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS); > > - if (!pos) > > - return false; > > - > > - pci_read_config_word(pdev, pos + PCI_ACS_CTRL,&ctrl); > > - if ((ctrl& acs_flags) != acs_flags) > > - return false; > > + return pci_acs_flags_enabled(pdev, acs_flags); > As I read 6.12.1.2, *if* a multifunction device supports peer-to-peer > traffic with another function(s), then certain ACS subfunctions > must be implemented. > So, I conclude from that statement (3rd bullet under this section), > if a MFD does not support peer-to-peer traffic, it doesn't have to provide > an ACS cap ... which is what I'm seeing in a number of MFD NICs (with sriov devices). > IOW, an MFD w/o an ACS cap == single function device w/o ACS cap. > > If that spec interpretation, and more importantly, hw implementation, is > correct, then won't above code return 'false' for an MFD with no ACS cap, > and shouldn't it return true in that case b/c it's optional/only-req'd > if MFD has peer-to-peer btwn functions? I read 6.12.1.2 as *if* a multifunction devices supports ACS, these are the things that it must support. Only if ACS is present could the lack of a capability imply a lack of peer-to-peer access. The intention in the code above is that a multifunction device without ACS will be treated as a peer-to-peer risk. That's no different than before. Effectively the only change from above is that we compare the full set of ACS bits on downstream ports, regardless of whether they're also multifunction. ACS wasn't added to the PCIe spec until 2.0, so PCIe 1.x compliant devices have no way to report for or against. If we had an example of a 2.x+ device that assumed lack of ACS means lack of peer-to-peer, perhaps we could go there, but then we're also expecting not only a PCIe capability, but a version that reflects something useful. That's probably too much to ask from hardware. Maybe there's another improvement in there to mask only the features supported by the capabilities of multifunction devices rather than a fixed mask, but that could be a follow-on if the interpretation makes sense. Thanks, Alex > > } > > > > + /* > > + * PCIe 3.0, 6.12.1.3 specifies no ACS capabilties are applicable > > + * to single function devices with the exception of downstream ports. > > + */ > > return true; > > } > > > > > > -- > > 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 > > -- > 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 ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2013-05-30 19:55 UTC | newest] Thread overview: 3+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2013-05-30 18:37 [PATCH] pci: Fix flaw in pci_acs_enabled() Alex Williamson 2013-05-30 19:35 ` Don Dutile 2013-05-30 19:55 ` Alex Williamson
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