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Commit cd12909c authored by David Vrabel's avatar David Vrabel Committed by Konrad Rzeszutek Wilk
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xen: map foreign pages for shared rings by updating the PTEs directly 



When mapping a foreign page with xenbus_map_ring_valloc() with the
GNTTABOP_map_grant_ref hypercall, set the GNTMAP_contains_pte flag and
pass a pointer to the PTE (in init_mm).

After the page is mapped, the usual fault mechanism can be used to
update additional MMs.  This allows the vmalloc_sync_all() to be
removed from alloc_vm_area().

Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Acked-by: default avatarAndrew Morton <akpm@linux-foundation.org>
[v1: Squashed fix by Michal for no-mmu case]
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: default avatarMichal Simek <monstr@monstr.eu>
parent 1ea6b8f4

arch/x86/xen/grant-table.c

+1 −1
Original line number Diff line number Diff line
@@ -71,7 +71,7 @@ int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes, 


	if (shared == NULL) {

		struct vm_struct *area =

			alloc_vm_area(PAGE_SIZE * max_nr_gframes);

			alloc_vm_area(PAGE_SIZE * max_nr_gframes, NULL);

		BUG_ON(area == NULL);

		shared = area->addr;

		*__shared = shared;

drivers/xen/xenbus/xenbus_client.c

+8 −3
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ 
#include <linux/vmalloc.h>

#include <linux/export.h>

#include <asm/xen/hypervisor.h>

#include <asm/xen/page.h>

#include <xen/interface/xen.h>

#include <xen/interface/event_channel.h>

#include <xen/events.h>
@@ -436,19 +437,20 @@ EXPORT_SYMBOL_GPL(xenbus_free_evtchn); 
int xenbus_map_ring_valloc(struct xenbus_device *dev, int gnt_ref, void **vaddr)

{

	struct gnttab_map_grant_ref op = {

		.flags = GNTMAP_host_map,

		.flags = GNTMAP_host_map | GNTMAP_contains_pte,

		.ref   = gnt_ref,

		.dom   = dev->otherend_id,

	};

	struct vm_struct *area;

	pte_t *pte;



	*vaddr = NULL;



	area = alloc_vm_area(PAGE_SIZE);

	area = alloc_vm_area(PAGE_SIZE, &pte);

	if (!area)

		return -ENOMEM;



	op.host_addr = (unsigned long)area->addr;

	op.host_addr = arbitrary_virt_to_machine(pte).maddr;



	if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))

		BUG();
@@ -527,6 +529,7 @@ int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr) 
	struct gnttab_unmap_grant_ref op = {

		.host_addr = (unsigned long)vaddr,

	};

	unsigned int level;



	/* It'd be nice if linux/vmalloc.h provided a find_vm_area(void *addr)

	 * method so that we don't have to muck with vmalloc internals here.
@@ -548,6 +551,8 @@ int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr) 
	}



	op.handle = (grant_handle_t)area->phys_addr;

	op.host_addr = arbitrary_virt_to_machine(

		lookup_address((unsigned long)vaddr, &level)).maddr;



	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))

		BUG();

include/linux/vmalloc.h

+1 −1
Original line number Diff line number Diff line
@@ -119,7 +119,7 @@ unmap_kernel_range(unsigned long addr, unsigned long size) 
#endif



/* Allocate/destroy a 'vmalloc' VM area. */

extern struct vm_struct *alloc_vm_area(size_t size);

extern struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes);

extern void free_vm_area(struct vm_struct *area);



/* for /dev/kmem */

mm/nommu.c

+1 −1
Original line number Diff line number Diff line
@@ -454,7 +454,7 @@ void __attribute__((weak)) vmalloc_sync_all(void) 
 *	between processes, it syncs the pagetable across all

 *	processes.

 */

struct vm_struct *alloc_vm_area(size_t size)

struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)

{

	BUG();

	return NULL;

mm/vmalloc.c

+13 −14
Original line number Diff line number Diff line
@@ -2141,23 +2141,30 @@ void __attribute__((weak)) vmalloc_sync_all(void) 


static int f(pte_t *pte, pgtable_t table, unsigned long addr, void *data)

{

	/* apply_to_page_range() does all the hard work. */

	pte_t ***p = data;



	if (p) {

		*(*p) = pte;

		(*p)++;

	}

	return 0;

}



/**

 *	alloc_vm_area - allocate a range of kernel address space

 *	@size:		size of the area

 *	@ptes:		returns the PTEs for the address space

 *

 *	Returns:	NULL on failure, vm_struct on success

 *

 *	This function reserves a range of kernel address space, and

 *	allocates pagetables to map that range.  No actual mappings

 *	are created.  If the kernel address space is not shared

 *	between processes, it syncs the pagetable across all

 *	processes.

 *	are created.

 *

 *	If @ptes is non-NULL, pointers to the PTEs (in init_mm)

 *	allocated for the VM area are returned.

 */

struct vm_struct *alloc_vm_area(size_t size)

struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)

{

	struct vm_struct *area;
@@ -2171,19 +2178,11 @@ struct vm_struct *alloc_vm_area(size_t size) 
	 * of kernel virtual address space and mapped into init_mm.

	 */

	if (apply_to_page_range(&init_mm, (unsigned long)area->addr,

				area->size, f, NULL)) {

				size, f, ptes ? &ptes : NULL)) {

		free_vm_area(area);

		return NULL;

	}



	/*

	 * If the allocated address space is passed to a hypercall

	 * before being used then we cannot rely on a page fault to

	 * trigger an update of the page tables.  So sync all the page

	 * tables here.

	 */

	vmalloc_sync_all();



	return area;

}

EXPORT_SYMBOL_GPL(alloc_vm_area);