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Re: [Xen-users] PCI Passthrough - Write-back to unknown field

  • To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • From: Radevici Ivan <ivan.radevici@xxxxxxxx>
  • Date: Thu, 27 Jul 2017 12:15:55 +0000
  • Accept-language: en-US, fi-FI
  • Cc: "xen-users@xxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxx>
  • Delivery-date: Thu, 27 Jul 2017 12:17:09 +0000
  • List-id: Xen user discussion <xen-users.lists.xen.org>
  • Thread-index: AQHTBqrV9a87movdbkmSphISXpMkDaJnKroAgABQ8AD//89ngIAARl/N
  • Thread-topic: [Xen-users] PCI Passthrough - Write-back to unknown field

>>On Thu, Jul 27, 2017 at 01:38:36PM +0300, Ivan Radevici wrote:
>> Thank you for your reply!
>> Here is the output of vcpu-list
>> sudo xl vcpu-list
>> Name                                ID  VCPU   CPU State   Time(s) Affinity
>> (Hard / Soft)
>> Domain-0                             0     0    0   -b-      75.7 0 / all
>> Domain-0                             0     1    1   r--      76.8 1 / all
>> win2k                                1     0    2   -b-      78.5 2 / all
>> win2k                                1     1    3   -b-      69.2 3 / all
>> but the card still fails the test. Also, it looks like cores are mainly in
>> idle, so probably problem is not there
> > While I was trying to pin vcpus I remembered about PV on HVM. There was a
>> chart somewhere in wiki, where it was shown that interrupts and timers have
>> poor performance on fully virtualised guests. This also may be a cause for
>> this behaviour. I am thinking about trying PVHVM (or just simple PV) drivers
>> for Windows2000, if I'll find some. How do you think, may it help?
>There's no such thing as PVHVM for Windows, this is only available for
>Linux/FreeBSD. AFAIK on Windows you can only add the PV drivers for
>block and network. Might be worth a try, but I doubt it's going to fix
>your PCI card issues.

I am not an expert in it, so I may be completely wrong, but at least there is a xenbus
driver, which "attaches to a virtual device on the PCI bus and provides child devices
for the other paravirtual device drivers to attach to." I understand that this will provide
interface only for the other virtual devices, but may be it will also somehow help.

>> Any other options?
>Try on another box maybe? Your box seems to be missing quite a lot of
>IOMMU features, so I guess it's kind of oldish hardware?

Yes, it is not the new one, but definitely not that old, to allow installation of
Win2k without virtualization

>Maybe on newer hardware you will no longer see the timeouts, although
>it's very hard to tell what's going on exactly without knowing what
>the driver is actually doing (or why it's failing exactly).

I already wrote to the NI support asking, what can be the cause of the error,
but still no response. Most probably, they'll just tell me that their cards
do not support virtualization

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