L4Android performance issue

[Adam Lackorzynski]

Hi,

On Wed Jul 11, 2012 at 21:42:59 -0500, Mai, Haohui wrote:
> >> I'm using an Eee PC which has an i945 chip. I tweaked my configuration
> >> a little bit but I still had no luck.
> >>
> >> There're two possible bugs(?) here:
> >>
> >> (1) The driver got confused because l4pci changes the func field of
> >> the pci table. The func field in PCI table is to describe whether
> >> there's another device attached to the slot. Here is code in Linux
> >> kernel causing problem:
> >>
> >>         gmch_device = pci_get_device(PCI_VENDOR_ID_INTEL, device, NULL);
> >>         if (gmch_device && PCI_FUNC(gmch_device->devfn) != 0) {
> >>                 gmch_device = pci_get_device(PCI_VENDOR_ID_INTEL,
> >>                                              device, gmch_device);
> >>         }
> >>
> >> On my machine, L4PCI reports the func field of my card (gmch_device in
> >> the code) as 1, which makes it find the "next" display card (i.e.,
> >> executing the if branch).
> >> Therefore it cannot find the device.
> >>
> >> I worked around it by disabling the if statement, and the kernel can
> >> detect the card and map in mmio memory.
> >
> > Are you using PCI_bus_ident() instead of PCI_bus() in your vbus config?
> >
> 
> I have PCI/CC_03 mapped in two caps, one in PCI_bus_ident() and one in
> PCI_bus(). I could try it out.

Just use one.

> >> (2) L4Linux is unable to execute "wbinvd" instruction. wbvind is a
> >> privileged instruction to write back all caches and invalidate them.
> >> The driver is executing this instruction at ring 3 -- thus generating
> >> a #GP fault.
> >>
> >> This is more troublesome and I don't really have a good idea of how to
> >> fix it. I appreciate if you can tell me the quickest way of fixing it.
> >
> > Looking at this a bit... this is just done for initializing the
> > ringbuffer which lives in non-caches memory already. It does not seem to
> > be used during runtime. There's also no comment why such a complete
> > global flush is required at all. Maybe to flush something else? Hmm. My
> > suggestion would thus just be to comment that out and see if it works
> > without.
> >
> >
> 
> There're a couple places that uses this instruction. I did try to
> disable the wbinvd instruction entirely but      it didn't work. So
> what do you think to take to implement it in L4Linux?

We're talking about flush_cache() in i810_main.h?
Anyway there seems to be some consensus that an interface for that might
be acceptable.


Adam
-- 
Adam                 adam at os.inf.tu-dresden.de
  Lackorzynski         http://os.inf.tu-dresden.de/~adam/