Re: [Qemu-devel] [PATCH 00/13] IOMMU: Enable interrupt remapping for Intel IOMMU

[Peter Xu]

Hi, Jan,

On Fri, Feb 19, 2016 at 07:46:26AM +0100, Jan Kiszka wrote:
> Hi Peter,
> 
> On 2016-02-19 04:30, Peter Xu wrote:
> > This patchset provide very basic functionalities for interrupt
> > remapping (IR) support of the emulated Intel IOMMU device.
> 
> Interesting. Some questions:
> 
> - Were you aware of
> http://git.kiszka.org/?p=qemu.git;a=shortlog;h=refs/heads/queues/vtd-intremap,
> and can you comment on how this relates to your approach? Mine included
> HPET support, e.g.

No. I do not know we have existing works related. I'd say that I am
one of those who are not fan of duplicating works. If I know that
there is existing ones, I would have asked you first.

Actually there are several people within my working team knows that
I would be working on this, and I believe none of us do know your
work too... Or there must be someone telling me so...

Whatever, I am sorry that finally we got some duplicated work. :-(

I have not go deeper into your codes yet, I'd say that most of the
logic is alike, since lots of works are to follow the spec. And the
implementation is slightly different (actually I just got this
memory region idea from Paolo yesterday... instead of a worse one to
declare a specific func ops for MSIs).

What I was going to do is to at least support:

- vhost
- pass through devices

So what I was planning is that, this series will be the start. And
the above two is the first-step goal (and I may need kvm-ioapic as
well though).

With the above, we should be able to run DPDK applications in guests
with either pass-through or vhost-user devices (these should be the
two scenario which is most possibly to be used AFAIU). This is what
I was trying to do. HPET is not with high priority in my todo list.

> 
> - Rita Sinha is currently working on integrating my old patches with the
> split-irqchip to get KVM working (as an Outreachy project). It's
> probably a bit unfortunate to consider a different horse that late in to
> project. What do you think, how could we benefit from each other?

I'd say that I am still new to QEMU community. So this is the first
time I encountered this kind of problem... Do you have any
suggestion?

> 
> - Radim was telling me to look on this as well. How do your efforts
> correlate?

Same as above. Do you have any suggestion on how we'd move on?

One question about your tree: have you posted patches before? and
what's the relationship between your tree and current QEMU master?

> 
> > 
> > By default, IR is disabled to be better compatible with current
> > QEMU. To enable IR, we can using the following command to boot a
> > IR-supported VM with basic network (still do not support kvm-ioapic,
> > so we need to specify kernel_irqchip=off here):
> > 
> > $ qemu-system-x86_64 -M q35,iommu=on,int_remap=on,kernel_irqchip=off \
> >      -enable-kvm -m 1024 -s \
> >      -monitor telnet::3333,server,nowait \
> >      -netdev user,id=user.0,hostfwd=tcp::5555-:22 \
> >      -device virtio-net-pci,netdev=user.0 \
> >      /var/lib/libvirt/images/vm1.qcow2
> > 
> > When guest boots, we can verify whether IR enabled by grepping the
> > dmesg like:
> > 
> > address@hidden ~]# journalctl -k | grep "DMAR-IR"
> > Feb 19 11:21:23 localhost.localdomain kernel: DMAR-IR: IOAPIC id 0 under 
> > DRHD base  0xfed90000 IOMMU 0
> > Feb 19 11:21:23 localhost.localdomain kernel: DMAR-IR: Enabled IRQ 
> > remapping in xapic mode
> > 
> > Currently only two devices are supported:
> > 
> > - Emulated IOAPIC device
> > - PCI Devices
> > 
> > TODO List:
> > 
> > - kvm-ioapic support
> > - vhost support
> > - pass through device support
> > - EIM support
> > - IR fault reporting
> > - source-id validation for IRTE
> > - IRTE cache and better queued invalidation
> > - migration support (for IOMMU as general?)
> > - more?
> > 
> > Peter Xu (13):
> >   q35: add "int-remap" flag to enable intr
> >   acpi: enable INTR for DMAR report structure
> >   intel_iommu: allow queued invalidation for IR
> >   intel_iommu: set IR bit for ECAP register
> >   acpi: add DMAR scope definition for root IOAPIC
> >   intel_iommu: define interrupt remap table addr register
> >   intel_iommu: handle interrupt remap enable
> >   intel_iommu: define several structs for IOMMU IR
> >   intel_iommu: provide helper function vtd_get_iommu
> >   ioapic-common: add iommu for IOAPICCommonState
> >   intel_iommu: add IR translation faults defines
> >   intel_iommu: ioapic: IR support for emulated IOAPIC
> >   intel_iommu: Add support for PCI MSI remap
> > 
> >  hw/core/machine.c                 |  20 ++
> >  hw/i386/acpi-build.c              |  41 +++-
> >  hw/i386/intel_iommu.c             | 397 
> > +++++++++++++++++++++++++++++++++++++-
> >  hw/i386/intel_iommu_internal.h    |  25 +++
> >  hw/intc/ioapic.c                  |  36 +++-
> >  hw/intc/ioapic_common.c           |   2 +
> >  hw/pci-host/q35.c                 |   6 +-
> >  include/hw/acpi/acpi-defs.h       |  15 ++
> >  include/hw/boards.h               |   1 +
> >  include/hw/i386/intel_iommu.h     | 121 ++++++++++++
> >  include/hw/i386/ioapic_internal.h |   3 +
> >  include/hw/pci/msi.h              |   4 +
> >  12 files changed, 651 insertions(+), 20 deletions(-)
> > 
> 
> Is there a git tree with your patches somewhere?

Currently not. If needed, I can try to create one. 

Thanks.
Peter

> 
> Thanks,
> Jan
>