[xen staging] x86/PV: drop a few misleading paging_mode_refcounts() checks

[patchbot@xxxxxxx]

commit cb79dc100fae7295009118ae10efe7822d5be2af
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Jul 31 17:40:13 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Jul 31 17:40:13 2020 +0200

    x86/PV: drop a few misleading paging_mode_refcounts() checks
    
    The filling and cleaning up of v->arch.guest_table in new_guest_cr3()
    was apparently inconsistent so far: There was a type ref acquired
    unconditionally for the new top level page table, but the dropping of
    the old type ref was conditional upon !paging_mode_refcounts(). Mirror
    this also to arch_set_info_guest().
    
    Also move new_guest_cr3()'s #ifdef to around the function - both callers
    now get built only when CONFIG_PV, i.e. no need to retain a stub.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Tim Deegan <tim@xxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/domain.c |  7 ++-----
 xen/arch/x86/mm.c     | 38 ++++++++++++++++----------------------
 2 files changed, 18 insertions(+), 27 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index fee6c3931a..f8084dc9e3 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1122,8 +1122,6 @@ int arch_set_info_guest(
 
     if ( !cr3_page )
         rc = -EINVAL;
-    else if ( paging_mode_refcounts(d) )
-        /* nothing */;
     else if ( cr3_page == v->arch.old_guest_table )
     {
         v->arch.old_guest_table = NULL;
@@ -1144,8 +1142,7 @@ int arch_set_info_guest(
         case -ERESTART:
             break;
         case 0:
-            if ( !compat && !VM_ASSIST(d, m2p_strict) &&
-                 !paging_mode_refcounts(d) )
+            if ( !compat && !VM_ASSIST(d, m2p_strict) )
                 fill_ro_mpt(cr3_mfn);
             break;
         default:
@@ -1166,7 +1163,7 @@ int arch_set_info_guest(
 
             if ( !cr3_page )
                 rc = -EINVAL;
-            else if ( !paging_mode_refcounts(d) )
+            else
             {
                 rc = get_page_type_preemptible(cr3_page, PGT_root_page_table);
                 switch ( rc )
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 82bc676553..638f6bf580 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -3149,9 +3149,9 @@ int vcpu_destroy_pagetables(struct vcpu *v)
     return rc;
 }
 
+#ifdef CONFIG_PV
 int new_guest_cr3(mfn_t mfn)
 {
-#ifdef CONFIG_PV
     struct vcpu *curr = current;
     struct domain *d = curr->domain;
     int rc;
@@ -3220,7 +3220,7 @@ int new_guest_cr3(mfn_t mfn)
 
     pv_destroy_ldt(curr); /* Unconditional TLB flush later. */
 
-    if ( !VM_ASSIST(d, m2p_strict) && !paging_mode_refcounts(d) )
+    if ( !VM_ASSIST(d, m2p_strict) )
         fill_ro_mpt(mfn);
     curr->arch.guest_table = pagetable_from_mfn(mfn);
     update_cr3(curr);
@@ -3231,30 +3231,24 @@ int new_guest_cr3(mfn_t mfn)
     {
         struct page_info *page = mfn_to_page(old_base_mfn);
 
-        if ( paging_mode_refcounts(d) )
-            put_page(page);
-        else
-            switch ( rc = put_page_and_type_preemptible(page) )
-            {
-            case -EINTR:
-            case -ERESTART:
-                curr->arch.old_guest_ptpg = NULL;
-                curr->arch.old_guest_table = page;
-                curr->arch.old_guest_table_partial = (rc == -ERESTART);
-                rc = -ERESTART;
-                break;
-            default:
-                BUG_ON(rc);
-                break;
-            }
+        switch ( rc = put_page_and_type_preemptible(page) )
+        {
+        case -EINTR:
+        case -ERESTART:
+            curr->arch.old_guest_ptpg = NULL;
+            curr->arch.old_guest_table = page;
+            curr->arch.old_guest_table_partial = (rc == -ERESTART);
+            rc = -ERESTART;
+            break;
+        default:
+            BUG_ON(rc);
+            break;
+        }
     }
 
     return rc;
-#else
-    ASSERT_UNREACHABLE();
-    return -EINVAL;
-#endif
 }
+#endif
 
 #ifdef CONFIG_PV
 static int vcpumask_to_pcpumask(
--
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