xen/m2p: do not reuse kmap_op->dev_bus_addr

commit 2fc136eecd0c647a6b13fcd00d0c41a1a28f35a5 upstream.

If the caller passes a valid kmap_op to m2p_add_override, we use
kmap_op->dev_bus_addr to store the original mfn, but dev_bus_addr is
part of the interface with Xen and if we are batching the hypercalls it
might not have been written by the hypervisor yet. That means that later
on Xen will write to it and we'll think that the original mfn is
actually what Xen has written to it.

Rather than "stealing" struct members from kmap_op, keep using
page->index to store the original mfn and add another parameter to
m2p_remove_override to get the corresponding kmap_op instead.
It is now responsibility of the caller to keep track of which kmap_op
corresponds to a particular page in the m2p_override (gntdev, the only
user of this interface that passes a valid kmap_op, is already doing that).

Reported-and-Tested-By: Sander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index c34f96c2f7a0773dae5fcd4a1e30f20eb477a83c..1bd321d00f261ea21cd33c3d40434fa34fbf4f90 100644 (file)
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -50,7 +50,8 @@ extern unsigned long set_phys_range_identity(unsigned long pfn_s,
 
 extern int m2p_add_override(unsigned long mfn, struct page *page,
                            struct gnttab_map_grant_ref *kmap_op);
-extern int m2p_remove_override(struct page *page, bool clear_pte);
+extern int m2p_remove_override(struct page *page,
+                               struct gnttab_map_grant_ref *kmap_op);
 extern struct page *m2p_find_override(unsigned long mfn);
 extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);
 

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 00a038540c8e4f4e34ee02e7330b3a10d74aea29..3ace817694783c81a0a56517bdd0b11152ab554e 100644 (file)
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -714,9 +714,6 @@ int m2p_add_override(unsigned long mfn, struct page *page,
 
                        xen_mc_issue(PARAVIRT_LAZY_MMU);
                }
-               /* let's use dev_bus_addr to record the old mfn instead */
-               kmap_op->dev_bus_addr = page->index;
-               page->index = (unsigned long) kmap_op;
        }
        spin_lock_irqsave(&m2p_override_lock, flags);
        list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);
@@ -743,7 +740,8 @@ int m2p_add_override(unsigned long mfn, struct page *page,
        return 0;
 }
 EXPORT_SYMBOL_GPL(m2p_add_override);
-int m2p_remove_override(struct page *page, bool clear_pte)
+int m2p_remove_override(struct page *page,
+               struct gnttab_map_grant_ref *kmap_op)
 {
        unsigned long flags;
        unsigned long mfn;
@@ -773,10 +771,8 @@ int m2p_remove_override(struct page *page, bool clear_pte)
        WARN_ON(!PagePrivate(page));
        ClearPagePrivate(page);
 
-       if (clear_pte) {
-               struct gnttab_map_grant_ref *map_op =
-                       (struct gnttab_map_grant_ref *) page->index;
-               set_phys_to_machine(pfn, map_op->dev_bus_addr);
+       set_phys_to_machine(pfn, page->index);
+       if (kmap_op != NULL) {
                if (!PageHighMem(page)) {
                        struct multicall_space mcs;
                        struct gnttab_unmap_grant_ref *unmap_op;
@@ -788,13 +784,13 @@ int m2p_remove_override(struct page *page, bool clear_pte)
                         * issued. In this case handle is going to -1 because
                         * it hasn't been modified yet.
                         */
-                       if (map_op->handle == -1)
+                       if (kmap_op->handle == -1)
                                xen_mc_flush();
                        /*
-                        * Now if map_op->handle is negative it means that the
+                        * Now if kmap_op->handle is negative it means that the
                         * hypercall actually returned an error.
                         */
-                       if (map_op->handle == GNTST_general_error) {
+                       if (kmap_op->handle == GNTST_general_error) {
                                printk(KERN_WARNING "m2p_remove_override: "
                                                "pfn %lx mfn %lx, failed to modify kernel mappings",
                                                pfn, mfn);
@@ -804,8 +800,8 @@ int m2p_remove_override(struct page *page, bool clear_pte)
                        mcs = xen_mc_entry(
                                        sizeof(struct gnttab_unmap_grant_ref));
                        unmap_op = mcs.args;
-                       unmap_op->host_addr = map_op->host_addr;
-                       unmap_op->handle = map_op->handle;
+                       unmap_op->host_addr = kmap_op->host_addr;
+                       unmap_op->handle = kmap_op->handle;
                        unmap_op->dev_bus_addr = 0;
 
                        MULTI_grant_table_op(mcs.mc,
@@ -816,10 +812,9 @@ int m2p_remove_override(struct page *page, bool clear_pte)
                        set_pte_at(&init_mm, address, ptep,
                                        pfn_pte(pfn, PAGE_KERNEL));
                        __flush_tlb_single(address);
-                       map_op->host_addr = 0;
+                       kmap_op->host_addr = 0;
                }
-       } else
-               set_phys_to_machine(pfn, page->index);
+       }
 
        /* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present
         * somewhere in this domain, even before being added to the

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 73f196ca713f20e037e22adccba64d0e00c936b1..c6decb901e5e16f4ba09ccef7db33675aeecb189 100644 (file)
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -337,7 +337,7 @@ static void xen_blkbk_unmap(struct pending_req *req)
                invcount++;
        }
 
-       ret = gnttab_unmap_refs(unmap, pages, invcount, false);
+       ret = gnttab_unmap_refs(unmap, NULL, pages, invcount);
        BUG_ON(ret);
 }
 

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 1ffd03bf8e10dcb6b015e3e0b94a2a460f0d0dcd..7f1241608489de05a33e957a77145f4faa605f0e 100644 (file)
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -314,8 +314,9 @@ static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
                }
        }
 
-       err = gnttab_unmap_refs(map->unmap_ops + offset, map->pages + offset,
-                               pages, true);
+       err = gnttab_unmap_refs(map->unmap_ops + offset,
+                       use_ptemod ? map->kmap_ops + offset : NULL, map->pages + offset,
+                       pages);
        if (err)
                return err;
 

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index f100ce20b16b428880863ab768bf952ed84c43a9..fda491cd53c106d43390e85920ea1df4e9a01617 100644 (file)
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -774,7 +774,8 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 EXPORT_SYMBOL_GPL(gnttab_map_refs);
 
 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
-                     struct page **pages, unsigned int count, bool clear_pte)
+                     struct gnttab_map_grant_ref *kmap_ops,
+                     struct page **pages, unsigned int count)
 {
        int i, ret;
 
@@ -786,7 +787,8 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
                return ret;
 
        for (i = 0; i < count; i++) {
-               ret = m2p_remove_override(pages[i], clear_pte);
+               ret = m2p_remove_override(pages[i], kmap_ops ?
+                                      &kmap_ops[i] : NULL);
                if (ret)
                        return ret;
        }

diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index 15f8a00ff003953639a4caba0e97109b8db06b36..f0037a89f7db3ed3ba0f49fc4c742059ba55ad6c 100644 (file)
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -185,6 +185,7 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
                    struct gnttab_map_grant_ref *kmap_ops,
                    struct page **pages, unsigned int count);
 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
-                     struct page **pages, unsigned int count, bool clear_pte);
+                     struct gnttab_map_grant_ref *kunmap_ops,
+                     struct page **pages, unsigned int count);
 
 #endif /* __ASM_GNTTAB_H__ */