On Sun, Jul 24, 2011 at 11:41:10AM +0300, Michael S. Tsirkin wrote:
> On Sun, Jul 24, 2011 at 11:12:44AM +0300, Michael S. Tsirkin wrote:
> > On Fri, Jul 22, 2011 at 02:35:47PM -0700, Chris Wright wrote:
> > > * Alex Williamson ([email protected]) wrote:
> > > > On Fri, 2011-07-22 at 14:24 -0700, Chris Wright wrote:
> > > > > * Donald Dutile ([email protected]) wrote:
> > > > > > diff --git a/hw/device-assignment.c b/hw/device-assignment.c
> > > > > > index 36ad6b0..34db52e 100644
> > > > > > --- a/hw/device-assignment.c
> > > > > > +++ b/hw/device-assignment.c
> > > > > > @@ -1419,16 +1419,18 @@ static int
> > > > > > assigned_device_pci_cap_init(PCIDevice *pci_dev)
> > > > > > }
> > > > > >
> > > > > > if ((pos = pci_find_cap_offset(pci_dev, PCI_CAP_ID_EXP, 0))) {
> > > > > > - uint8_t version;
> > > > > > + uint8_t version, size;
> > > > > > uint16_t type, devctl, lnkcap, lnksta;
> > > > > > uint32_t devcap;
> > > > > > - int size = 0x3c; /* version 2 size */
> > > > > >
> > > > > > version = pci_get_byte(pci_dev->config + pos +
> > > > > > PCI_EXP_FLAGS);
> > > > > > version &= PCI_EXP_FLAGS_VERS;
> > > > > > if (version == 1) {
> > > > > > size = 0x14;
> > > > > > - } else if (version > 2) {
> > > > > > + } else if (version == 2) {
> > > > > > + /* don't include slot cap/stat/ctrl 2 regs; only
> > > > > > support endpoints */
> > > > > > + size = 0x34;
> > > > >
> > > > > That doesn't look correct to me. The size is fixed, just that some
> > > > > registers are Reserved Zero when they do not apply (e.g. endpoint
> > > > > only).
> > > >
> > > > Apparently it can be interpreted differently. In this case, we've seen
> > > > a tg3 device expose a v2 PCI express capability at offset 0xcc. Using
> > > > 0x3c bytes, we extend 8 bytes past the legacy config space area :(
> > >
> > > Wow, that device sounds broken to me. The spec is pretty clear.
> >
> > Yes, I agree it's broken. Looks like something that
> > happens when a device is designed in parallel with the spec.
> >
> > What bothers me is this patch seems to make devices that do behave
> > correctly out of spec (registers will be writeable by default) -
> > correct?
> >
> > How about we check for overflow and only do the hacks
> > if it happens?
> >
> > Also, the code to initialize slot and root control registers is still
> > there: it would seem that running it will corrupt memmory beyond the
> > config array?
>
> I take this last bit back: registers we touch are at offset < 0x34.
> Sorry about the noise. But the question about read-only registers
> still stands.
Also, where does the magic 0x34 come from? I'm guessing this is
simply what's left till the end of the config space.
So let's be conservative specific as possible with
this hack:
/* A version 2 device was observed to only have a partial
* implementation for the capability structure. Apparently, it doesn't
* implement the registers from slot capability 2 and on (offset 0x34),
* with the capability at offset 0xCC = 256 - 0x34. This is out of spec,
* but let's try to support this. */
if (version == 2 && pos == 0xCC) {
size = 0x34;
}
> >
> > --
> > MST
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