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powerpc/pci: mmap anonymous memory when legacy_mem doesn't exist 

The new legacy_mem file in sysfs is causing problems with X on machines
that don't support legacy memory access. The way I initially implemented
it, we would fail with -ENXIO when trying to mmap it, thus exposing to
X that we do support the API but there is no legacy memory.

Unfortunately, X poor error handling is causing it to fail to start when
it gets this error.

This implements a workaround hack that instead maps anonymous memory
instead (using shmem if VM_SHARED is set, just like /dev/zero does).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Benjamin Herrenschmidt 2009-02-08 14:27:21 +00:00
parent d87bf76679
commit 5b11abfdb5
1 changed files with 15 additions and 2 deletions
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17
arch/powerpc/kernel/pci-common.c
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@ -561,8 +561,21 @@ int pci_mmap_legacy_page_range(struct pci_bus *bus,
(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;