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Commit da503fa6 authored by Jan Beulich's avatar Jan Beulich Committed by Dave Airlie
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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: default avatarDave Airlie <airlied@redhat.com>
parent dcd981a7

drivers/char/agp/backend.c

+8 −8
Original line number Diff line number Diff line
@@ -188,10 +188,10 @@ static int agp_backend_initialize(struct agp_bridge_data *bridge) 


err_out:

	if (bridge->driver->needs_scratch_page) {

		bridge->driver->agp_destroy_page(gart_to_virt(bridge->scratch_page_real),

						 AGP_PAGE_DESTROY_UNMAP);

		bridge->driver->agp_destroy_page(gart_to_virt(bridge->scratch_page_real),

						 AGP_PAGE_DESTROY_FREE);

		void *va = gart_to_virt(bridge->scratch_page_real);



		bridge->driver->agp_destroy_page(va, AGP_PAGE_DESTROY_UNMAP);

		bridge->driver->agp_destroy_page(va, AGP_PAGE_DESTROY_FREE);

	}

	if (got_gatt)

		bridge->driver->free_gatt_table(bridge);
@@ -215,10 +215,10 @@ static void agp_backend_cleanup(struct agp_bridge_data *bridge) 


	if (bridge->driver->agp_destroy_page &&

	    bridge->driver->needs_scratch_page) {

		bridge->driver->agp_destroy_page(gart_to_virt(bridge->scratch_page_real),

						 AGP_PAGE_DESTROY_UNMAP);

		bridge->driver->agp_destroy_page(gart_to_virt(bridge->scratch_page_real),

						 AGP_PAGE_DESTROY_FREE);

		void *va = gart_to_virt(bridge->scratch_page_real);



		bridge->driver->agp_destroy_page(va, AGP_PAGE_DESTROY_UNMAP);

		bridge->driver->agp_destroy_page(va, AGP_PAGE_DESTROY_FREE);

	}

}

drivers/char/agp/generic.c

+5 −2
Original line number Diff line number Diff line
@@ -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);

drivers/char/agp/intel-agp.c

+4 −2
Original line number Diff line number Diff line
@@ -418,9 +418,11 @@ static void intel_i810_free_by_type(struct agp_memory *curr) 
		if (curr->page_count == 4)

			i8xx_destroy_pages(gart_to_virt(curr->memory[0]));

		else {

			agp_bridge->driver->agp_destroy_page(gart_to_virt(curr->memory[0]),

			void *va = gart_to_virt(curr->memory[0]);



			agp_bridge->driver->agp_destroy_page(va,

							     AGP_PAGE_DESTROY_UNMAP);

			agp_bridge->driver->agp_destroy_page(gart_to_virt(curr->memory[0]),

			agp_bridge->driver->agp_destroy_page(va,

							     AGP_PAGE_DESTROY_FREE);

		}

		agp_free_page_array(curr);