| Message ID | 20141121220833.31095.12371.stgit@gimli.home (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On Fri, 21 Nov 2014, Alex Williamson wrote: > For the most part multivector MSI is not supported and drivers and > hardware wanting multiple vectors opt for MSI-X instead. It seems > though that having the ability to query the arch/platform code to > determine whether allocating multiple MSI vectors will ever succeed > is a useful thing. For instance, vfio-pci can use this to determine > whether to expose multiple MSI vectors to the user. If we know we > cannot ever support more than one vector, we have a better shot at > the userspace driver working, especially if it's a guest OS, if we > only expose one vector as being available in the interface. > > Signed-off-by: Alex Williamson <alex.williamson@redhat.com> > --- > > drivers/pci/msi.c | 5 +++++ > include/linux/msi.h | 1 + > 2 files changed, 6 insertions(+) > > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c > index 9fab30a..36b503a 100644 > --- a/drivers/pci/msi.c > +++ b/drivers/pci/msi.c > @@ -79,6 +79,11 @@ int __weak arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type) > return 0; > } > > +bool __weak arch_supports_multivector_msi(struct pci_dev *dev) Please not another weak arch function. We are in the process to reduce them not to extend them. arch_supports is pretty much wrong here anyway. We are moving away from arch MSI dependencies simply because it's not a arch property per se. Multi MSI is a property of the underlying interrupt controllers and there might be several MSI interrupt domains on a given system. They can or cannot support multi MSI. The current x86 implementation is a tangled maze and Jiang is in the process to distangle it completely. Until thats done x86 is not going to add new ad hoc interfaces. Once we converted everything over to the new hierarchical irqdomains we can add such an interface to the code, but for now I'm not accepting anything like that into x86 msi related code. Thanks, tglx -- 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 Sun, 2014-11-23 at 21:20 +0100, Thomas Gleixner wrote: > On Fri, 21 Nov 2014, Alex Williamson wrote: > > For the most part multivector MSI is not supported and drivers and > > hardware wanting multiple vectors opt for MSI-X instead. It seems > > though that having the ability to query the arch/platform code to > > determine whether allocating multiple MSI vectors will ever succeed > > is a useful thing. For instance, vfio-pci can use this to determine > > whether to expose multiple MSI vectors to the user. If we know we > > cannot ever support more than one vector, we have a better shot at > > the userspace driver working, especially if it's a guest OS, if we > > only expose one vector as being available in the interface. > > > > Signed-off-by: Alex Williamson <alex.williamson@redhat.com> > > --- > > > > drivers/pci/msi.c | 5 +++++ > > include/linux/msi.h | 1 + > > 2 files changed, 6 insertions(+) > > > > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c > > index 9fab30a..36b503a 100644 > > --- a/drivers/pci/msi.c > > +++ b/drivers/pci/msi.c > > @@ -79,6 +79,11 @@ int __weak arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type) > > return 0; > > } > > > > +bool __weak arch_supports_multivector_msi(struct pci_dev *dev) > > Please not another weak arch function. We are in the process to reduce > them not to extend them. > > arch_supports is pretty much wrong here anyway. We are moving away > from arch MSI dependencies simply because it's not a arch property per > se. > > Multi MSI is a property of the underlying interrupt controllers and > there might be several MSI interrupt domains on a given system. They > can or cannot support multi MSI. > > The current x86 implementation is a tangled maze and Jiang is in the > process to distangle it completely. Until thats done x86 is not going > to add new ad hoc interfaces. > > Once we converted everything over to the new hierarchical irqdomains > we can add such an interface to the code, but for now I'm not > accepting anything like that into x86 msi related code. Ok, I guess I can do some ugliness with associating the IOMMU IRQ remapping capability with multivector MSI support within an #ifdef x86 block. Gross, but I think that's as accurate as I can get w/o a hook through the MSI code. Is there any target for the refactoring you mention? Thanks, Alex -- 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 2014/11/25 5:45, Alex Williamson wrote: > On Sun, 2014-11-23 at 21:20 +0100, Thomas Gleixner wrote: >> On Fri, 21 Nov 2014, Alex Williamson wrote: >>> For the most part multivector MSI is not supported and drivers and >>> hardware wanting multiple vectors opt for MSI-X instead. It seems >>> though that having the ability to query the arch/platform code to >>> determine whether allocating multiple MSI vectors will ever succeed >>> is a useful thing. For instance, vfio-pci can use this to determine >>> whether to expose multiple MSI vectors to the user. If we know we >>> cannot ever support more than one vector, we have a better shot at >>> the userspace driver working, especially if it's a guest OS, if we >>> only expose one vector as being available in the interface. >>> >>> Signed-off-by: Alex Williamson <alex.williamson@redhat.com> >>> --- >>> >>> drivers/pci/msi.c | 5 +++++ >>> include/linux/msi.h | 1 + >>> 2 files changed, 6 insertions(+) >>> >>> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c >>> index 9fab30a..36b503a 100644 >>> --- a/drivers/pci/msi.c >>> +++ b/drivers/pci/msi.c >>> @@ -79,6 +79,11 @@ int __weak arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type) >>> return 0; >>> } >>> >>> +bool __weak arch_supports_multivector_msi(struct pci_dev *dev) >> >> Please not another weak arch function. We are in the process to reduce >> them not to extend them. >> >> arch_supports is pretty much wrong here anyway. We are moving away >> from arch MSI dependencies simply because it's not a arch property per >> se. >> >> Multi MSI is a property of the underlying interrupt controllers and >> there might be several MSI interrupt domains on a given system. They >> can or cannot support multi MSI. >> >> The current x86 implementation is a tangled maze and Jiang is in the >> process to distangle it completely. Until thats done x86 is not going >> to add new ad hoc interfaces. >> >> Once we converted everything over to the new hierarchical irqdomains >> we can add such an interface to the code, but for now I'm not >> accepting anything like that into x86 msi related code. > > Ok, I guess I can do some ugliness with associating the IOMMU IRQ > remapping capability with multivector MSI support within an #ifdef x86 > block. Gross, but I think that's as accurate as I can get w/o a hook > through the MSI code. Is there any target for the refactoring you > mention? Thanks, Hi Alex, The hierarchy irqdomain framework and some preparation work for PCI MSI refactor will be merged into v3.19, there are already in tip tree. If thing goes smoothly, we may finish PCI MSI refactoring on x86 platform for the merging window after 3.19, not sure 3.20 or 4.0:) Regards! Gerry > > Alex > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- 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/msi.c b/drivers/pci/msi.c index 9fab30a..36b503a 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -79,6 +79,11 @@ int __weak arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type) return 0; } +bool __weak arch_supports_multivector_msi(struct pci_dev *dev) +{ + return false; +} + /* * We have a default implementation available as a separate non-weak * function, as it is used by the Xen x86 PCI code diff --git a/include/linux/msi.h b/include/linux/msi.h index 44f4746..2365c64 100644 --- a/include/linux/msi.h +++ b/include/linux/msi.h @@ -58,6 +58,7 @@ void arch_teardown_msi_irq(unsigned int irq); int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type); void arch_teardown_msi_irqs(struct pci_dev *dev); void arch_restore_msi_irqs(struct pci_dev *dev); +bool arch_supports_multivector_msi(struct pci_dev *dev); void default_teardown_msi_irqs(struct pci_dev *dev); void default_restore_msi_irqs(struct pci_dev *dev);
For the most part multivector MSI is not supported and drivers and hardware wanting multiple vectors opt for MSI-X instead. It seems though that having the ability to query the arch/platform code to determine whether allocating multiple MSI vectors will ever succeed is a useful thing. For instance, vfio-pci can use this to determine whether to expose multiple MSI vectors to the user. If we know we cannot ever support more than one vector, we have a better shot at the userspace driver working, especially if it's a guest OS, if we only expose one vector as being available in the interface. Signed-off-by: Alex Williamson <alex.williamson@redhat.com> --- drivers/pci/msi.c | 5 +++++ include/linux/msi.h | 1 + 2 files changed, 6 insertions(+) -- 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