The machine_to_phys_mapping array needs updating during page-in, and
during page deallocation. If a page is gone, a call to
get_gpfn_from_mfn will still return the old gfn for an already paged-out
page. This happens when the entire guest ram is paged-out before
xen_vga_populate_vram() runs. Then XENMEM_populate_physmap is called
with gfn 0xff000. A new page is allocated with alloc_domheap_pages.
This new page does not have a gfn yet. However, in
guest_physmap_add_entry() the passed mfn maps still to an old gfn
(perhaps from another old guest). This old gfn is in paged-out state in
this guests context and has no mfn anymore. As a result, the ASSERT()
triggers because p2m_is_ram() is true for p2m_ram_paging* types.
If the machine_to_phys_mapping array is updated properly, both loops in
guest_physmap_add_entry() turn into no-ops for the new page and the
mfn/gfn mapping will be done at the end of the function.
The same thing needs to happen dring a page-in, the current gfn must be
written for the page.
If XENMEM_add_to_physmap is used with XENMAPSPACE_gmfn,
get_gpfn_from_mfn() will return an appearently valid gfn. As a result,
guest_physmap_remove_page() is called. The ASSERT in p2m_remove_page
triggers because the passed mfn does not match the old mfn for the
passed gfn.
Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
---
v3:
invalidate machine_to_phys_mapping[] during page deallocation
v2:
call set_gpfn_from_mfn only if mfn is valid
---
xen/arch/x86/mm/p2m.c | 15 +++++++++++----
xen/common/page_alloc.c | 9 +++++++++
2 files changed, 20 insertions(+), 4 deletions(-)
--- xen-unstable.hg-4.1.22433.orig/xen/arch/x86/mm/p2m.c
+++ xen-unstable.hg-4.1.22433/xen/arch/x86/mm/p2m.c
@@ -2825,10 +2825,17 @@ void p2m_mem_paging_resume(struct p2m_do
/* Fix p2m entry */
mfn = gfn_to_mfn(p2m, rsp.gfn, &p2mt);
- p2m_lock(p2m);
- set_p2m_entry(p2m, rsp.gfn, mfn, 0, p2m_ram_rw);
- audit_p2m(p2m, 1);
- p2m_unlock(p2m);
+ if ( mfn_valid(mfn) )
+ {
+ p2m_lock(p2m);
+ set_p2m_entry(p2m, rsp.gfn, mfn, 0, p2m_ram_rw);
+ set_gpfn_from_mfn(mfn_x(mfn), rsp.gfn);
+ audit_p2m(p2m, 1);
+ p2m_unlock(p2m);
+ } else {
+ gdprintk(XENLOG_ERR, "invalid mfn %lx for gfn %lx p2mt %x flags %lx\n",
+ mfn_x(mfn), rsp.gfn, p2mt, (unsigned long)rsp.flags);
+ }
/* Unpause domain */
if ( rsp.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
--- xen-unstable.hg-4.1.22433.orig/xen/common/page_alloc.c
+++ xen-unstable.hg-4.1.22433/xen/common/page_alloc.c
@@ -1199,9 +1199,18 @@ void free_domheap_pages(struct page_info
{
int i, drop_dom_ref;
struct domain *d = page_get_owner(pg);
+ unsigned long mfn;
ASSERT(!in_irq());
+ /* this page is not a gfn anymore */
+ mfn = page_to_mfn(pg);
+ if ( mfn_valid(mfn) )
+ {
+ for ( i = 0; i < (1 << order); i++ )
+ set_gpfn_from_mfn(mfn + i, INVALID_M2P_ENTRY);
+ }
+
if ( unlikely(is_xen_heap_page(pg)) )
{
/* NB. May recursively lock from relinquish_memory(). */
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