From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: [PATCH 1/3] PCI/MSI: Initial hook for archs to declare multivector MSI support Date: Fri, 21 Nov 2014 15:08:33 -0700 Message-ID: <20141121220833.31095.12371.stgit@gimli.home> References: <20141121213752.31095.30735.stgit@gimli.home> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20141121213752.31095.30735.stgit-GCcqpEzw8uZBDLzU/O5InQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org Cc: linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org, tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org List-Id: iommu@lists.linux-foundation.org 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 --- 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) +{ + 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);