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Groups > linux.kernel > #1240506
| From | Vlad Zolotarov <vladz@cloudius-systems.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support |
| Date | 2015-10-06 16:50 +0200 |
| Message-ID | <qgBJ0-Em-31@gated-at.bofh.it> (permalink) |
| References | (2 earlier) <qg4tH-3lu-1@gated-at.bofh.it> <qg9jJ-1RW-37@gated-at.bofh.it> <qgaz8-3zT-5@gated-at.bofh.it> <qgbbQ-4yg-9@gated-at.bofh.it> <qgBzk-sN-21@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 10/06/15 17:38, Michael S. Tsirkin wrote: > On Mon, Oct 05, 2015 at 01:20:11PM +0300, Avi Kivity wrote: >> On 10/05/2015 12:49 PM, Greg KH wrote: >>> On Mon, Oct 05, 2015 at 11:28:03AM +0300, Avi Kivity wrote: >>>> Of course it has to be documented, but this just follows vfio. >>>> >>>> Eventfd is a natural enough representation of an interrupt; both kvm and >>>> vfio use it, and are also able to share the eventfd, allowing a vfio >>>> interrupt to generate a kvm interrupt, without userspace intervention, and >>>> one day without even kernel intervention. >>> That's nice and wonderful, but it's not how UIO works today, so this is >>> now going to be a mix and match type interface, with no justification so >>> far as to why to create this new api and exactly how this is all going >>> to be used from userspace. >> The intended user is dpdk (http://dpdk.org), which is a family of userspace >> networking drivers for high performance networking applications. >> >> The natural device driver for dpdk is vfio, which both provides memory >> protection and exposes msi/msix interrupts. However, in many cases vfio >> cannot be used, either due to the lack of an iommu (for example, in >> virtualized environments) or out of a desire to avoid the iommus performance >> impact. >> >> The challenge in exposing msix interrupts to user space is that there are >> many of them, so you can't simply poll the device fd. If you do, how do you >> know which interrupt was triggered? The solution that vfio adopted was to >> associate each interrupt with an eventfd, allowing it to be individually >> polled. Since you can pass an eventfd with SCM_RIGHTS, and since kvm can >> trigger guest interrupts using an eventfd, the solution is very flexible. >> >>> Example code would be even better... >>> >>> >> >> This is the vfio dpdk interface code: >> >> http://dpdk.org/browse/dpdk/tree/lib/librte_eal/linuxapp/eal/eal_pci_vfio.c >> >> basically, the equivalent uio msix code would be very similar if uio adopts >> a similar interface: >> >> http://dpdk.org/browse/dpdk/tree/lib/librte_eal/linuxapp/eal/eal_pci_uio.c >> >> (current code lacks msi/msix support, of course). > So you really want a driver that behaves exactly like vfio. > Which immediately begs a question: why not extend vfio > to cover your usecase. The only "like VFIO" behavior we implement here is binding the MSI-X interrupt notification to eventfd descriptor. This doesn't justifies the hassle of implementing IOMMU-less VFIO mode. > -- 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/
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Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-06 16:40 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-06 16:50 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-06 17:00 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-06 17:30 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-06 17:30 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Alex Williamson <alex.williamson@redhat.com> - 2015-10-06 21:00 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Stephen Hemminger <stephen@networkplumber.org> - 2015-10-06 23:40 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Alex Williamson <alex.williamson@redhat.com> - 2015-10-06 23:50 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-07 10:00 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-07 10:10 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-07 10:10 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-07 09:00 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-07 18:40 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-07 23:10 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 06:20 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 09:50 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 10:00 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 11:40 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 11:50 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 14:20 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-08 07:40 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 09:40 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-08 10:50 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 11:20 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-08 11:50 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 14:10 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 14:30 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 15:30 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 15:30 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 18:50 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 19:10 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 19:40 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 20:00 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Greg KH <gregkh@linuxfoundation.org> - 2015-10-08 20:40 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 10:40 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 11:00 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-08 11:20 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 12:30 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-08 15:30 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 16:20 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Alex Williamson <alex.williamson@redhat.com> - 2015-10-08 17:40 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Alex Williamson <alex.williamson@redhat.com> - 2015-10-07 18:40 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-07 22:10 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-07 10:00 +0200
Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 10:50 +0200
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