From: Jan Beulich <jbeulich@suse.com>
Date: Mon, 27 Oct 2014 15:43:12 +0000 (+0100)
Subject: x86: tolerate running on EFI runtime services page tables in map_domain_page()
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~4124
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https:/%22bookmarks://%22/%22http:/www.example.com/cgi/%22https:/%22bookmarks:/%22?a=commitdiff_plain;h=e65436ba36be8f1b735573d8fc9af7d8a053ba5f;p=xen.git

x86: tolerate running on EFI runtime services page tables in map_domain_page()

In the event of a #PF while in an EFI runtime service function we
otherwise can't dump the page tables, making the analysis of the
problem more cumbersome.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
---

diff --git a/xen/arch/x86/domain_page.c b/xen/arch/x86/domain_page.c
index 3903952d2d..158a1645d7 100644
--- a/xen/arch/x86/domain_page.c
+++ b/xen/arch/x86/domain_page.c
@@ -7,6 +7,7 @@
  */
 
 #include <xen/domain_page.h>
+#include <xen/efi.h>
 #include <xen/mm.h>
 #include <xen/perfc.h>
 #include <xen/pfn.h>
@@ -37,11 +38,14 @@ static inline struct vcpu *mapcache_current_vcpu(void)
      */
     if ( unlikely(pagetable_is_null(v->arch.guest_table)) && is_pv_vcpu(v) )
     {
+        unsigned long cr3;
+
         /* If we really are idling, perform lazy context switch now. */
         if ( (v = idle_vcpu[smp_processor_id()]) == current )
             sync_local_execstate();
         /* We must now be running on the idle page table. */
-        ASSERT(read_cr3() == __pa(idle_pg_table));
+        ASSERT((cr3 = read_cr3()) == __pa(idle_pg_table) ||
+               (efi_enabled && cr3 == efi_rs_page_table()));
     }
 
     return v;
diff --git a/xen/arch/x86/efi/stub.c b/xen/arch/x86/efi/stub.c
index 8916a2ec7b..b8f49f873d 100644
--- a/xen/arch/x86/efi/stub.c
+++ b/xen/arch/x86/efi/stub.c
@@ -9,6 +9,12 @@ const bool_t efi_enabled = 0;
 
 void __init efi_init_memory(void) { }
 
+paddr_t efi_rs_page_table(void)
+{
+    BUG();
+    return 0;
+}
+
 unsigned long efi_get_time(void)
 {
     BUG();
diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c
index 1c43d109fc..553ff91702 100644
--- a/xen/common/efi/runtime.c
+++ b/xen/common/efi/runtime.c
@@ -98,6 +98,11 @@ void efi_rs_leave(unsigned long cr3)
     stts();
 }
 
+paddr_t efi_rs_page_table(void)
+{
+    return virt_to_maddr(efi_l4_pgtable);
+}
+
 unsigned long efi_get_time(void)
 {
     EFI_TIME time;
diff --git a/xen/include/xen/efi.h b/xen/include/xen/efi.h
index 8a2b78892d..5e02724572 100644
--- a/xen/include/xen/efi.h
+++ b/xen/include/xen/efi.h
@@ -28,6 +28,7 @@ struct xenpf_efi_runtime_call;
 struct compat_pf_efi_runtime_call;
 
 void efi_init_memory(void);
+paddr_t efi_rs_page_table(void);
 unsigned long efi_get_time(void);
 void efi_halt_system(void);
 void efi_reset_system(bool_t warm);