Hi,
> > * I'd like to see some more flexibility in the pci bar layout. Stuff
> > I have in mind:
> > - New devices which don't need a legacy bar can use bar 0 for
> > modern.
> > - One MMIO bar is enough, we can place both virtio regions and
> > msi-x regions there. I'd suggest to add msi-x sub-regions to
> > the modern bar.
>
> Why exactly? It seems simpler to separate things, extra BARs
> have no cost.
Well, there are only six BARs. legacy bar, modern mmio bar, msi-x bar,
modern io bar (for fast isr). That already four out of six ...
We have a mmio bar, which we partition into subregions for virtio-1.0
anyway. Also placing msi-x there is a single msix_init() call. xhci is
doing that too:
00000000febf0000-00000000febf3fff (prio 1, RW): xhci
00000000febf0000-00000000febf003f (prio 0, RW): capabilities
00000000febf0040-00000000febf043f (prio 0, RW): operational
00000000febf0440-00000000febf044f (prio 0, RW): usb3 port #1
00000000febf0450-00000000febf045f (prio 0, RW): usb3 port #2
00000000febf0460-00000000febf046f (prio 0, RW): usb3 port #3
00000000febf0470-00000000febf047f (prio 0, RW): usb3 port #4
00000000febf0480-00000000febf048f (prio 0, RW): usb2 port #1
00000000febf0490-00000000febf049f (prio 0, RW): usb2 port #2
00000000febf04a0-00000000febf04af (prio 0, RW): usb2 port #3
00000000febf04b0-00000000febf04bf (prio 0, RW): usb2 port #4
00000000febf1000-00000000febf121f (prio 0, RW): runtime
00000000febf2000-00000000febf281f (prio 0, RW): doorbell
00000000febf3000-00000000febf30ff (prio 0, RW): msix-table
00000000febf3800-00000000febf3807 (prio 0, RW): msix-pba
> > * What is the reason for making the modern bar 8M in size? Looks a bit
> > excessive, given that only 64k or so of that are actually used ...
>
> I use a page per VQ for architectures that can locate the offset of the
> accessed page that triggered EPT violation faster than the offset within
> page. I think this is the case for SVM.
8M still looks excessive, given that we typically have a small number of
queues per device. Do you allocate address space for the maximum
possible number of queues unconditionally?
> > virtio-scsi seems to be broken, at least my usual fedora guest didn't
> > boot up from virtio-scsi disk when using a guest kernel with this patch
> > series applied.
>
> I'll re-test. Do other devices work for you? Thanks!
Didn't came very far yet in my testing due to the guest not booting. I
plan to try other storage for the image, but didn't found the time yet.
I've tried to boot a F21 live iso with virtio-net (legacy guest driver
obviously), which seems to work ok in light testing.
BTW: is there a tool (or pciutils patch) which can decode the virtio
capabilities?
cheers,
Gerd
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