From: Alex Williamson <alex.williamson@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Avi Kivity <avi@redhat.com>, Sheng Yang <sheng@linux.intel.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
kvm@vger.kernel.org
Subject: Re: [PATCH 0/8][v2] MSI-X mask emulation support for assigned device
Date: Wed, 20 Oct 2010 09:12:38 -0600 [thread overview]
Message-ID: <1287587558.3007.31.camel@x201> (raw)
In-Reply-To: <20101020145822.GC22204@redhat.com>
On Wed, 2010-10-20 at 16:58 +0200, Michael S. Tsirkin wrote:
> On Wed, Oct 20, 2010 at 08:58:38AM -0600, Alex Williamson wrote:
> > On Wed, 2010-10-20 at 15:43 +0200, Michael S. Tsirkin wrote:
> > > On Wed, Oct 20, 2010 at 12:59:42PM +0200, Avi Kivity wrote:
> > > > How far away is vfio? If it's merged soon, we might avoid making
> > > > changes to the old assigned device infrastructure and instead update
> > > > vfio.
> > >
> > > Hard to be sure, hopefully 2.6.38 material.
> > >
> > > Some issues off the top of my head are
> > > - readonly/virtualized table correctness
> > > hopefully will start converging now that
> > > we are switching to standard registers from pci_regs.h
> > > - work out some capability negotiation mechanism so userspace/kernel
> > > can detect bug fixes/missing features and recover or fail gracefully
> > > - with multiple assigned devices in a guest:
> > > I don't think we have figured out how do they share an iommu context
> >
> > A single UIOMMU fd can be used for multiple devices. The code I wrote
> > supports this, but it's really only meant to support a uiommufd passed
> > via the command line for libvirt usage. Since libvirt doesn't yet
> > support vfio, it's never been tested.
>
> I think there was some issue that programming was
> done through vfio fd and got lost if you try to hot unplug
> device which programmed it. Maybe I'm wrong ...
Hasn't been tested, so bugs are probably. Sounds fixable though.
Sharing an IOMMU context is at least part of the design.
> > > - maybe: reset handling (flr support) - need to look a it
> >
> > I'd add that for the qemu vfio driver, we need to work out the KVM
> > interrupt optimizations, otherwise we suffer extra latency vs current
> > code.
>
> You see this in some benchmark?
I haven't done any formal benchmarks on VFIO, but I recall that while
both can achieve line rate on a 1G link, VFIO currently requires more
CPU to do so. Bouncing interrupts through QEMU seems like an obvious
candidate for that. Thanks,
Alex
next prev parent reply other threads:[~2010-10-20 15:12 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-20 8:26 [PATCH 0/8][v2] MSI-X mask emulation support for assigned device Sheng Yang
2010-10-20 8:26 ` [PATCH 1/8] PCI: MSI: Move MSI-X entry definition to pci_regs.h Sheng Yang
2010-10-20 11:07 ` Matthew Wilcox
2010-10-20 8:26 ` [PATCH 2/8] irq: Export irq_to_desc() to modules Sheng Yang
2010-10-20 8:26 ` [PATCH 3/8] KVM: x86: Enable ENABLE_CAP capability for x86 Sheng Yang
2010-10-20 8:26 ` [PATCH 4/8] KVM: Move struct kvm_io_device to kvm_host.h Sheng Yang
2010-10-20 8:26 ` [PATCH 5/8] KVM: Add kvm_get_irq_routing_entry() func Sheng Yang
2010-10-20 8:53 ` Avi Kivity
2010-10-20 8:58 ` Sheng Yang
2010-10-20 9:13 ` Sheng Yang
2010-10-20 9:17 ` Sheng Yang
2010-10-20 9:32 ` Avi Kivity
2010-10-20 8:26 ` [PATCH 6/8] KVM: assigned dev: Preparation for mask support in userspace Sheng Yang
2010-10-20 9:30 ` Avi Kivity
2010-10-22 14:53 ` Marcelo Tosatti
2010-10-24 12:19 ` Sheng Yang
2010-10-24 12:23 ` Michael S. Tsirkin
2010-10-28 8:21 ` Sheng Yang
2010-10-20 8:26 ` [PATCH 7/8] KVM: assigned dev: Introduce io_device for MSI-X MMIO accessing Sheng Yang
2010-10-20 9:46 ` Avi Kivity
2010-10-20 10:33 ` Michael S. Tsirkin
2010-10-21 6:46 ` Sheng Yang
2010-10-21 9:27 ` Avi Kivity
2010-10-21 9:24 ` Michael S. Tsirkin
2010-10-21 9:47 ` Avi Kivity
2010-10-21 10:51 ` Michael S. Tsirkin
2010-10-20 22:35 ` Michael S. Tsirkin
2010-10-21 7:44 ` Sheng Yang
2010-10-20 8:26 ` [PATCH 8/8] KVM: Emulation MSI-X mask bits for assigned devices Sheng Yang
2010-10-20 9:49 ` Avi Kivity
2010-10-20 22:24 ` Michael S. Tsirkin
2010-10-21 8:30 ` Sheng Yang
2010-10-21 8:39 ` Michael S. Tsirkin
2010-10-22 4:42 ` Sheng Yang
2010-10-22 10:17 ` Michael S. Tsirkin
2010-10-22 13:30 ` Sheng Yang
2010-10-22 14:32 ` Michael S. Tsirkin
2010-10-20 9:51 ` [PATCH 0/8][v2] MSI-X mask emulation support for assigned device Avi Kivity
2010-10-20 10:44 ` Michael S. Tsirkin
2010-10-20 10:59 ` Avi Kivity
2010-10-20 13:43 ` Michael S. Tsirkin
2010-10-20 14:58 ` Alex Williamson
2010-10-20 14:58 ` Michael S. Tsirkin
2010-10-20 15:12 ` Alex Williamson [this message]
2010-10-20 15:17 ` Avi Kivity
2010-10-20 15:22 ` Alex Williamson
2010-10-20 15:26 ` Avi Kivity
2010-10-20 15:38 ` Alex Williamson
2010-10-20 14:47 ` Alex Williamson
2010-10-20 14:46 ` Michael S. Tsirkin
2010-10-20 15:07 ` Alex Williamson
2010-10-20 15:13 ` Michael S. Tsirkin
2010-10-20 20:13 ` Alex Williamson
2010-10-20 22:06 ` Michael S. Tsirkin
2010-10-20 15:23 ` Avi Kivity
2010-10-20 15:38 ` Alex Williamson
2010-10-20 15:54 ` Avi Kivity
2010-10-20 15:59 ` Michael S. Tsirkin
2010-10-20 16:13 ` Avi Kivity
2010-10-20 17:11 ` Michael S. Tsirkin
2010-10-20 18:31 ` Alex Williamson
2010-10-21 7:41 ` Sheng Yang
2010-10-20 19:02 ` Marcelo Tosatti
2010-10-21 7:10 ` Sheng Yang
2010-10-21 8:21 ` Michael S. Tsirkin
2010-10-20 22:20 ` Michael S. Tsirkin
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