Messages in this thread | | | From | Thomas Gleixner <> | Subject | RE: Virtualizing MSI-X on IMS via VFIO | Date | Thu, 24 Jun 2021 03:36:07 +0200 |
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Kevin,
On Thu, Jun 24 2021 at 00:00, Kevin Tian wrote: >> From: Alex Williamson <alex.williamson@redhat.com> >> Sent: Wednesday, June 23, 2021 11:20 PM >> > [...] > > > So the only downside today of allocating more MSI-X vectors than >> > necessary is memory consumption for the irq descriptors. >> >> As above, this is a QEMU policy of essentially trying to be a good >> citizen and allocate only what we can infer the guest is using. What's >> a good way for QEMU, or any userspace, to know it's running on a host >> where vector exhaustion is not an issue? > > In my proposal a new command (VFIO_DEVICE_ALLOC_IRQS) is > introduced to separate allocation from enabling. The availability > of this command could be the indicator whether vector > exhaustion is not an issue now?
Your proposal still does not address the fundamental issue of a missing feedback to the guest and you can invent a gazillion more IOCTL commands and none of them will solve that issue. A hypercall/paravirt interface is the only reasonable solution.
The time you are wasting to come up with non-solutions would have surely been better spent implementing the already known and obvious proper solution. You might be halfways done already with that.
Thanks,
tglx
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