Commit ee072640 authored by Stefano Stabellini's avatar Stefano Stabellini Committed by Konrad Rzeszutek Wilk
Browse files

xen/m2p: use GNTTABOP_unmap_and_replace to reinstate the original mapping 



GNTTABOP_unmap_grant_ref unmaps a grant and replaces it with a 0
mapping instead of reinstating the original mapping.
Doing so separately would be racy.

To unmap a grant and reinstate the original mapping atomically we use
GNTTABOP_unmap_and_replace.
GNTTABOP_unmap_and_replace doesn't work with GNTMAP_contains_pte, so
don't use it for kmaps.  GNTTABOP_unmap_and_replace zeroes the mapping
passed in new_addr so we have to reinstate it, however that is a
per-cpu mapping only used for balloon scratch pages, so we can be sure that
it's not going to be accessed while the mapping is not valid.

Signed-off-by: default avatarStefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Acked-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: alex@alex.org.uk
CC: dcrisan@flexiant.com

[v1: Konrad fixed up the conflicts]
Conflicts:
	arch/x86/xen/p2m.c
parent 072b2064

arch/x86/xen/p2m.c

+15 −6
Original line number Diff line number Diff line
@@ -161,6 +161,7 @@ 
#include <asm/xen/page.h>

#include <asm/xen/hypercall.h>

#include <asm/xen/hypervisor.h>

#include <xen/balloon.h>

#include <xen/grant_table.h>



#include "multicalls.h"
@@ -967,7 +968,10 @@ int m2p_remove_override(struct page *page, 
	if (kmap_op != NULL) {

		if (!PageHighMem(page)) {

			struct multicall_space mcs;

			struct gnttab_unmap_grant_ref *unmap_op;

			struct gnttab_unmap_and_replace *unmap_op;

			struct page *scratch_page = get_balloon_scratch_page();

			unsigned long scratch_page_address = (unsigned long)

				__va(page_to_pfn(scratch_page) << PAGE_SHIFT);



			/*

			 * It might be that we queued all the m2p grant table
@@ -990,20 +994,25 @@ int m2p_remove_override(struct page *page, 
			}



			mcs = xen_mc_entry(

					sizeof(struct gnttab_unmap_grant_ref));

					sizeof(struct gnttab_unmap_and_replace));

			unmap_op = mcs.args;

			unmap_op->host_addr = kmap_op->host_addr;

			unmap_op->new_addr = scratch_page_address;

			unmap_op->handle = kmap_op->handle;

			unmap_op->dev_bus_addr = 0;



			MULTI_grant_table_op(mcs.mc,

					GNTTABOP_unmap_grant_ref, unmap_op, 1);

					GNTTABOP_unmap_and_replace, unmap_op, 1);



			xen_mc_issue(PARAVIRT_LAZY_MMU);



			set_pte_at(&init_mm, address, ptep,

					pfn_pte(pfn, PAGE_KERNEL));

			mcs = __xen_mc_entry(0);

			MULTI_update_va_mapping(mcs.mc, scratch_page_address,

					pfn_pte(page_to_pfn(get_balloon_scratch_page()),

					PAGE_KERNEL_RO), 0);

			xen_mc_issue(PARAVIRT_LAZY_MMU);



			kmap_op->host_addr = 0;

			put_balloon_scratch_page();

		}

	}

drivers/xen/gntdev.c

+2 −9
Original line number Diff line number Diff line
@@ -272,19 +272,12 @@ static int map_grant_pages(struct grant_map *map) 
		 * with find_grant_ptes.

		 */

		for (i = 0; i < map->count; i++) {

			unsigned level;

			unsigned long address = (unsigned long)

				pfn_to_kaddr(page_to_pfn(map->pages[i]));

			pte_t *ptep;

			u64 pte_maddr = 0;

			BUG_ON(PageHighMem(map->pages[i]));



			ptep = lookup_address(address, &level);

			pte_maddr = arbitrary_virt_to_machine(ptep).maddr;

			gnttab_set_map_op(&map->kmap_ops[i], pte_maddr,

				map->flags |

				GNTMAP_host_map |

				GNTMAP_contains_pte,

			gnttab_set_map_op(&map->kmap_ops[i], address,

				map->flags | GNTMAP_host_map,

				map->grants[i].ref,

				map->grants[i].domid);

		}

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