[xen master] x86/shadow: simplify conditionals in sh_{get,put}_ref()

[patchbot@xxxxxxx]

commit e4fb1750487b296858dfd6f9ed3c306b25100388
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Jan 9 14:26:12 2023 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Jan 9 14:26:12 2023 +0100

    x86/shadow: simplify conditionals in sh_{get,put}_ref()
    
    In both cases the "entry_pa != 0" check is redundant; storing 0 when the
    field already is 0 is quite fine. Move the cheaper remaining part first
    in sh_get_ref(). In sh_put_ref() convert the has-up-pointer check into
    an assertion (requiring the zero check to be retained there).
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/mm/shadow/private.h | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/mm/shadow/private.h b/xen/arch/x86/mm/shadow/private.h
index 2c2c18985d..e5329e0d0c 100644
--- a/xen/arch/x86/mm/shadow/private.h
+++ b/xen/arch/x86/mm/shadow/private.h
@@ -583,9 +583,7 @@ static inline int sh_get_ref(struct domain *d, mfn_t smfn, 
paddr_t entry_pa)
     sp->u.sh.count = nx;
 
     /* We remember the first shadow entry that points to each shadow. */
-    if ( entry_pa != 0
-         && sh_type_has_up_pointer(d, sp->u.sh.type)
-         && sp->up == 0 )
+    if ( !sp->up && sh_type_has_up_pointer(d, sp->u.sh.type) )
         sp->up = entry_pa;
 
     return 1;
@@ -604,10 +602,11 @@ static inline void sh_put_ref(struct domain *d, mfn_t 
smfn, paddr_t entry_pa)
     ASSERT(!(sp->count_info & PGC_count_mask));
 
     /* If this is the entry in the up-pointer, remove it */
-    if ( entry_pa != 0
-         && sh_type_has_up_pointer(d, sp->u.sh.type)
-         && sp->up == entry_pa )
+    if ( sp->up == entry_pa )
+    {
+        ASSERT(!entry_pa || sh_type_has_up_pointer(d, sp->u.sh.type));
         sp->up = 0;
+    }
 
     x = sp->u.sh.count;
     nx = x - 1;
--
generated by git-patchbot for /home/xen/git/xen.git#master