Re: [Bug #12608] 2.6.29-rc powerpc G5 Xorg legacy_mem regression

Benjamin Herrenschmidt
2009-02-07T02:51:12Z

> I still don't understand the point of this legacy_mem file at all,
> and why X should want to mmap it, if it works so well when it's
> thus divorced from reality. But I won't worry my pretty little
> head over it any further - please don't waste your time trying
> to explain it to me!

VGA memory hole :-) ie, text mode & fonts

Ben.

> Thanks,
> Hugh
>
> >
> > Index: linux-work/arch/powerpc/kernel/pci-common.c
> > ===================================================================
> > --- linux-work.orig/arch/powerpc/kernel/pci-common.c 2009-02-06 16:23:36.000000000 +1100
> > +++ linux-work/arch/powerpc/kernel/pci-common.c 2009-02-06 16:30:32.000000000 +1100
> > @@ -561,8 +561,21 @@ int pci_mmap_legacy_page_range(struct pc
> > (unsigned long long)(offset + size - 1));
> >
> > if (mmap_state == pci_mmap_mem) {
> > - if ((offset + size) > hose->isa_mem_size)
> > - return -ENXIO;
> > + /* Hack alert !
> > + *
> > + * Because X is lame and can fail starting if it gets an error trying
> > + * to mmap legacy_mem (instead of just moving on without legacy memory
> > + * access) we fake it here by giving it anonymous memory, effectively
> > + * behaving just like /dev/zero
> > + */
> > + if ((offset + size) > hose->isa_mem_size) {
> > + printk(KERN_DEBUG
> > + "Process %s (pid:%d) mapped non-existing PCI legacy memory for 0%04x:%02x\n",
> > + current->comm, current->pid, pci_domain_nr(bus), bus->number);
> > + if (vma->vm_flags & VM_SHARED)
> > + return shmem_zero_setup(vma);
> > + return 0;
> > + }
> > offset += hose->isa_mem_phys;
> > } else {
> > unsigned long io_offset = (unsigned long)hose->io_base_virt - _IO_BASE;