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>
diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index 19b12d2..0f41812 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -561,8 +561,21 @@
(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;