From ee0726407feaf504dff304fb603652fb2d778b42 Mon Sep 17 00:00:00 2001 From: Stefano Stabellini Date: Tue, 23 Jul 2013 17:23:54 +0000 Subject: [PATCH] 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: Stefano Stabellini Reviewed-by: David Vrabel Acked-by: Konrad Rzeszutek Wilk CC: alex@alex.org.uk CC: dcrisan@flexiant.com [v1: Konrad fixed up the conflicts] Conflicts: arch/x86/xen/p2m.c --- arch/x86/xen/p2m.c | 21 +++++++++++++++------ drivers/xen/gntdev.c | 11 ++--------- 2 files changed, 17 insertions(+), 15 deletions(-) diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c index 74672ee..0d4ec35 100644 --- a/arch/x86/xen/p2m.c +++ b/arch/x86/xen/p2m.c @@ -161,6 +161,7 @@ #include #include #include +#include #include #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(); } } diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index eab5427..e41c79c 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -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); } -- 2.7.4