x86 hvm: implement HVMOP_pagetable_dying

This patch implements HVMOP_pagetable_dying: an hypercall for
guests to notify Xen that a pagetable is about to be destroyed so that
Xen can use it as a hint to unshadow the pagetable soon and unhook the
top-level user-mode shadow entries right away.

Gianluca Guida is the original author of this patch.

Signed-off-by: Gianluca Guida <glguida@gmail.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/xen/include/asm-x86/paging.h b/xen/include/asm-x86/paging.h
index fca130b43a..10aa9f1339 100644
--- a/xen/include/asm-x86/paging.h
+++ b/xen/include/asm-x86/paging.h
@@ -95,6 +95,7 @@ struct shadow_paging_mode {
     void          (*destroy_monitor_table )(struct vcpu *v, mfn_t mmfn);
     int           (*guess_wrmap           )(struct vcpu *v, 
                                             unsigned long vaddr, mfn_t gmfn);
+    void          (*pagetable_dying       )(struct vcpu *v, paddr_t gpa);
     /* For outsiders to tell what mode we're in */
     unsigned int shadow_levels;
 };
@@ -342,6 +343,10 @@ static inline void paging_write_p2m_entry(struct domain *d, unsigned long gfn,
         safe_write_pte(p, new);
 }
 
+/* Called from the guest to indicate that the a process is being
+ * torn down and its pagetables will soon be discarded */
+void pagetable_dying(struct domain *d, paddr_t gpa);
+
 /* Print paging-assistance info to the console */
 void paging_dump_domain_info(struct domain *d);
 void paging_dump_vcpu_info(struct vcpu *v);