[xen staging] x86/P2M: allow 2M superpage use for shadowed guests

[patchbot@xxxxxxx]

commit f2d947ac0738098ec2f52a17448df7e2acd64ff9
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Aug 18 09:29:34 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Aug 18 09:29:34 2022 +0200

    x86/P2M: allow 2M superpage use for shadowed guests
    
    For guests in shadow mode the P2M table gets used only by software. The
    only place where it matters whether superpages in the P2M can be dealt
    with is sh_unshadow_for_p2m_change(): The table is never made accessible
    to hardware for address translation, and the only checks of _PAGE_PSE in
    P2M entries in shadow code are in this function (all others are against
    guest page table entries). That function has been capable of handling
    them even before commit 0ca1669871f8a ("P2M: check whether hap mode is
    enabled before using 2mb pages") disabled 2M use in this case for
    dubious reasons ("potential errors when hap is disabled").
    
    While doing this, move "order" into more narrow scope and replace the
    local variable "d" by a new "hap" one.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Tim Deegan <tim@xxxxxxx>
---
 xen/arch/x86/mm/p2m.c | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index a2446f0c41..a405ee5fde 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -403,28 +403,22 @@ struct page_info *p2m_get_page_from_gfn(
 int p2m_set_entry(struct p2m_domain *p2m, gfn_t gfn, mfn_t mfn,
                   unsigned int page_order, p2m_type_t p2mt, p2m_access_t p2ma)
 {
-    struct domain *d = p2m->domain;
+    bool hap = hap_enabled(p2m->domain);
     unsigned long todo = 1ul << page_order;
-    unsigned int order;
     int set_rc, rc = 0;
 
     ASSERT(gfn_locked_by_me(p2m, gfn));
 
     while ( todo )
     {
-        if ( hap_enabled(d) )
-        {
-            unsigned long fn_mask = !mfn_eq(mfn, INVALID_MFN) ? mfn_x(mfn) : 0;
-
-            fn_mask |= gfn_x(gfn) | todo;
-
-            order = (!(fn_mask & ((1ul << PAGE_ORDER_1G) - 1)) &&
-                     hap_has_1gb) ? PAGE_ORDER_1G :
-                    (!(fn_mask & ((1ul << PAGE_ORDER_2M) - 1)) &&
-                     hap_has_2mb) ? PAGE_ORDER_2M : PAGE_ORDER_4K;
-        }
-        else
-            order = 0;
+        unsigned long fn_mask = (!mfn_eq(mfn, INVALID_MFN) ? mfn_x(mfn) : 0) |
+                                gfn_x(gfn) | todo;
+        unsigned int order = (!(fn_mask & ((1ul << PAGE_ORDER_1G) - 1)) &&
+                              hap && hap_has_1gb)
+                             ? PAGE_ORDER_1G
+                             : (!(fn_mask & ((1ul << PAGE_ORDER_2M) - 1)) &&
+                                (!hap || hap_has_2mb))
+                               ? PAGE_ORDER_2M : PAGE_ORDER_4K;
 
         set_rc = p2m->set_entry(p2m, gfn, mfn, order, p2mt, p2ma, -1);
         if ( set_rc )
--
generated by git-patchbot for /home/xen/git/xen.git#staging