From: Thomas Gleixner <tglx@linutronix.de>
To: "Tian\, Kevin" <kevin.tian@intel.com>,
Alex Williamson <alex.williamson@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>, "Dey\,
Megha" <megha.dey@intel.com>, "Raj\, Ashok" <ashok.raj@intel.com>,
"Pan\, Jacob jun" <jacob.jun.pan@intel.com>, "Jiang\,
Dave" <dave.jiang@intel.com>, "Liu\, Yi L" <yi.l.liu@intel.com>,
"Lu\, Baolu" <baolu.lu@intel.com>, "Williams\,
Dan J" <dan.j.williams@intel.com>, "Luck\,
Tony" <tony.luck@intel.com>, "Kumar\,
Sanjay K" <sanjay.k.kumar@intel.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>,
Kirti Wankhede <kwankhede@nvidia.com>,
Peter Zijlstra <peterz@infradead.org>,
Marc Zyngier <maz@kernel.org>, Bjorn Helgaas <helgaas@kernel.org>
Subject: RE: Virtualizing MSI-X on IMS via VFIO
Date: Thu, 24 Jun 2021 03:36:07 +0200 [thread overview]
Message-ID: <87r1gsavso.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <MWHPR11MB18864420ACE88E060203F7818C079@MWHPR11MB1886.namprd11.prod.outlook.com>
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
next prev parent reply other threads:[~2021-06-24 1:36 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-22 10:16 Virtualizing MSI-X on IMS via VFIO Tian, Kevin
2021-06-22 15:50 ` Dave Jiang
2021-06-23 6:16 ` Tian, Kevin
2021-06-22 19:12 ` Alex Williamson
2021-06-22 23:59 ` Thomas Gleixner
2021-06-23 6:12 ` Tian, Kevin
2021-06-23 16:31 ` Thomas Gleixner
2021-06-23 16:41 ` Jason Gunthorpe
2021-06-23 23:41 ` Tian, Kevin
2021-06-23 23:37 ` Tian, Kevin
2021-06-24 1:18 ` Thomas Gleixner
2021-06-24 2:41 ` Tian, Kevin
2021-06-24 15:14 ` Thomas Gleixner
2021-06-24 21:44 ` Alex Williamson
2021-06-25 5:21 ` Tian, Kevin
2021-06-25 8:43 ` Thomas Gleixner
2021-06-25 12:42 ` Thomas Gleixner
2021-06-25 21:19 ` Thomas Gleixner
2021-06-25 8:29 ` Thomas Gleixner
2021-06-24 17:03 ` Jacob Pan
2021-06-23 15:19 ` Alex Williamson
2021-06-24 0:00 ` Tian, Kevin
2021-06-24 1:36 ` Thomas Gleixner [this message]
2021-06-24 2:20 ` Thomas Gleixner
2021-06-24 2:48 ` Alex Williamson
2021-06-24 12:06 ` [PATCH] vfio/pci: Document the MSI[X] resize side effects properly Thomas Gleixner
2021-06-24 22:22 ` Alex Williamson
2021-06-24 17:52 ` Virtualizing MSI-X on IMS via VFIO Alex Williamson
2021-06-24 0:43 ` Thomas Gleixner
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