Re: [Xen-devel] qemu-xen-dir + PCI passthrough = BOOM

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Sun, 26 Jan 2014, Zhang, Yang Z wrote:
> Anthony PERARD wrote on 2014-01-09:
> > On Wed, Jan 08, 2014 at 02:44:51PM -0500, Konrad Rzeszutek Wilk wrote:
> >> On Wed, Dec 18, 2013 at 02:48:24PM +0000, Anthony PERARD wrote:
> >>> On Mon, Dec 16, 2013 at 10:08:16AM -0500, Konrad Rzeszutek Wilk wrote:
> >>>> On Fri, Dec 06, 2013 at 04:03:10PM +0000, Wei Liu wrote:
> >>>>> On Fri, Dec 06, 2013 at 04:00:18PM +0000, Wei Liu wrote:
> >>>>> [...]
> >>>>>>> Those Xen report something like:
> >>>>>>> (XEN) page_alloc.c:1460:d0 Over-allocation for domain 46:
> >>>>>>> 131329 >
> >>>>>>> 131328
> >>>>>>> (XEN) memory.c:132:d0 Could not allocate order=0 extent:
> >>>>>>> id=46
> >>>>>>> memflags=0 (62 of 64)
> >>>>>>> 
> >>>>>>> ?
> >>>>>>> 
> >>>>>>> (I tryied to reproduce the issue by simply add many
> >>>>>>> emulated
> >>>>>>> e1000 in QEMU :) )
> >>>>>>> 
> >>> 
> >>>> -bash-4.1# lspci -s 01:00.0 -v
> >>>> 01:00.0 Ethernet controller: Intel Corporation 82576 Gigabit
> >>>> Network
> > Connection (rev 01)
> >>>>         Subsystem: Intel Corporation Gigabit ET Dual Port Server
> >>>>         Adapter Flags: fast devsel, IRQ 16 Memory at fbc20000
> >>>>         (32-bit, non-prefetchable) [disabled] [size=128K] Memory at
> >>>>         fb800000 (32-bit, non-prefetchable) [disabled] [size=4M] I/O
> >>>>         ports at e020 [disabled] [size=32] Memory at fbc44000
> >>>>         (32-bit, non-prefetchable) [disabled] [size=16K] Expansion
> >>>>         ROM at fb400000 [disabled] [size=4M]
> >>> 
> >>> BTW, I think this is the issue, the Expansion ROM. qemu-xen will
> >>> allocate memory for it. Will have maybe have to find another way.
> >>> qemu-trad those not seems to allocate memory, but I haven't been
> >>> very far in trying to check that.
> >> 
> >> And indeed that is the case. The "Fix" below fixes it.
> >> 
> >> 
> >> Based on that and this guest config:
> >> disk = [ 'file:/mnt/lab/latest/root_image.iso,hdc:cdrom,r']
> >> memory = 2048
> >> boot="d"
> >> maxvcpus=32
> >> vcpus=1
> >> serial='pty'
> >> vnclisten="0.0.0.0"
> >> name="latest"
> >> vif = [ 'mac=00:0F:4B:00:00:68, bridge=switch' ] pci = ["01:00.0"]
> >> 
> >> I can boot the guest.
> > 
> > And can you access the ROM from the guest ?
> > 
> > 
> > Also, I have another patch, it will initialize the PCI ROM BAR like any 
> > other BAR.
> > In this case, if qemu is envolved in the access to ROM, it will print
> > an error, like it the case for other BAR.
> > 
> > I tried to test it, but it was with an embedded VGA card. When I dump
> > the ROM, I got the same one as the emulated card instead of the ROM from 
> > the device.
> > 
> > 
> > diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c index 6dd7a68..2bbdb6d
> > 100644 --- a/hw/xen/xen_pt.c +++ b/hw/xen/xen_pt.c @@ -440,8 +440,8 @@
> > static int xen_pt_register_regions(XenPCIPassthroughState *s)
> > 
> >          s->bases[PCI_ROM_SLOT].access.maddr = d->rom.base_addr;
> > -        memory_region_init_rom_device(&s->rom, OBJECT(s), NULL, NULL,
> > -                                      "xen-pci-pt-rom", d->rom.size);
> > +        memory_region_init_io(&s->rom, OBJECT(s), &ops, &s->dev,
> > +                              "xen-pci-pt-rom", d->rom.size);
> >          pci_register_bar(&s->dev, PCI_ROM_SLOT,
> > PCI_BASE_ADDRESS_MEM_PREFETCH,
> >                           &s->rom);
> >
> 
> Hi, Anthony,
> 
> Does your fixing is the final solution for this issue? If yes, will you push 
> it before Xen 4.4 release?

I included this patch in the last pull request I sent to Anthony
Liguori:

http://marc.info/?l=qemu-devel&m=138997319906095

It hasn't been pulled yet, but I would expect that it is going to be
upstream soon.
Regarding the 4.4 release, we are trying to fix a couple of other
serious bugs in the qemu-xen tree right now, but it is still conceivable
to have this fix backported to the tree in time for the release.

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