agp: two-stage page destruction issue

besides it apparently being useful only in 2.6.24 (the changes in 2.6.25
really mean that it could be converted back to a single-stage mechanism),
I'm seeing an issue in Xen Dom0 kernels, which is caused by the calling
of gart_to_virt() in the second stage invocations of the destroy function.
I think that besides this being a real issue with Xen (where
unmap_page_from_agp() is not just a page table attribute change), this
also is invalid from a theoretical perspective: One should not assume that
gart_to_virt() is still valid after unmapping a page. So minimally (keeping
the 2-stage mechanism) a patch like the one below would be needed.

Jan

Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/char/agp/generic.c b/drivers/char/agp/generic.c
index 7fc0c99a3a58..b6650a63197d 100644
--- a/drivers/char/agp/generic.c
+++ b/drivers/char/agp/generic.c
@@ -202,10 +202,13 @@ void agp_free_memory(struct agp_memory *curr)
 	}
 	if (curr->page_count != 0) {
 		for (i = 0; i < curr->page_count; i++) {
-			curr->bridge->driver->agp_destroy_page(gart_to_virt(curr->memory[i]), AGP_PAGE_DESTROY_UNMAP);
+			curr->memory[i] = (unsigned long)gart_to_virt(curr->memory[i]);
+			curr->bridge->driver->agp_destroy_page((void *)curr->memory[i],
+							       AGP_PAGE_DESTROY_UNMAP);
 		}
 		for (i = 0; i < curr->page_count; i++) {
-			curr->bridge->driver->agp_destroy_page(gart_to_virt(curr->memory[i]), AGP_PAGE_DESTROY_FREE);
+			curr->bridge->driver->agp_destroy_page((void *)curr->memory[i],
+							       AGP_PAGE_DESTROY_FREE);
 		}
 	}
 	agp_free_key(curr->key);