[vfio-users] about vfio interrupt performance

[James]

Hi Experts:

Sorry to disturb you.



I failed to find any valid data about vfio interrupt performance in
community, so send mail to you boldly.



We have a pcie device work on x86 platform, and no VM in our env,  I plan
to replace the kernel side device driver with vfio framework, reimplement
it in user space after enable vfio/vfio_pci/vfio_iommu_type1 in kernel. The
original intention is just to get rid of the dependents to kernel, let our
application which need to access our pcie device to be a pure application,
let it can run on other linux distribution(no custom kernel driver need).



Our pcie device have the following character:

1, have a great deal of interrupt when working

2, and also have high demand to interrupt’s processing speed.

3, it will need to access almost all bar space after mapping.



Here want to check with you, compare with previous kernel side device
driver, if there are huge decrease for interrupt’s processing speed when
the interrupt numbers are huge in short time?

How about your comments to my this attemptation, if it’s valueble to move
driver to userspace in this kind of situation(no vm, huge interrupt numbers
etc..).







BTW, I found there are some random issue when using vfio in community, such
as:

1, Some device’s extend configuration space will have problem when
accessing by random.

2, When try to access the device’s space which in the same iommu groups at
the same time, it will trigger issue by random.



If this kind of issue have relation with IOMMU’s hardware limitation, or if
we can bypass it via some method for now?





Many thanks for your times!!


Best regards!

James
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