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From: Jan Beulich <jbeulich@suse.com>
To: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>,
	"George Dunlap" <george.dunlap@citrix.com>,
	"Tim Deegan" <tim@xen.org>
Subject: [PATCH v4 2/3] x86/shadow: re-use variables in shadow_get_page_from_l1e()
Date: Fri, 23 Apr 2021 12:53:24 +0200	[thread overview]
Message-ID: <a7817f29-9a07-ab20-2224-999e75537fe3@suse.com> (raw)
In-Reply-To: <3e7ad009-f062-d58a-9380-103ce1573a73@suse.com>

There's little point in doing multiple mfn_to_page() or page_get_owner()
on all the same MFN. Calculate them once at the start of the function.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Tim Deegan <tim@xen.org>
---
v5: Integrate into series. Re-base.
v2: Re-base.

--- a/xen/arch/x86/mm/shadow/set.c
+++ b/xen/arch/x86/mm/shadow/set.c
@@ -88,19 +88,25 @@ static int inline
 shadow_get_page_from_l1e(shadow_l1e_t sl1e, struct domain *d, p2m_type_t type)
 {
     int res;
-    mfn_t mfn;
-    struct domain *owner;
+    mfn_t mfn = shadow_l1e_get_mfn(sl1e);
+    const struct page_info *pg = NULL;
+    struct domain *owner = NULL;
 
     ASSERT(!sh_l1e_is_magic(sl1e));
     ASSERT(shadow_mode_refcounts(d));
 
+    if ( mfn_valid(mfn) )
+    {
+        pg = mfn_to_page(mfn);
+        owner = page_get_owner(pg);
+    }
+
     /*
      * Check whether refcounting is suppressed on this page. For example,
      * VMX'es APIC access MFN is just a surrogate page.  It doesn't actually
      * get accessed, and hence there's no need to refcount it.
      */
-    mfn = shadow_l1e_get_mfn(sl1e);
-    if ( mfn_valid(mfn) && page_refcounting_suppressed(mfn_to_page(mfn)) )
+    if ( pg && page_refcounting_suppressed(pg) )
         return 0;
 
     res = get_page_from_l1e(sl1e, d, d);
@@ -111,9 +117,7 @@ shadow_get_page_from_l1e(shadow_l1e_t sl
      */
     if ( unlikely(res < 0) &&
          !shadow_mode_translate(d) &&
-         mfn_valid(mfn = shadow_l1e_get_mfn(sl1e)) &&
-         (owner = page_get_owner(mfn_to_page(mfn))) &&
-         (d != owner) )
+         owner && (d != owner) )
     {
         res = xsm_priv_mapping(XSM_TARGET, d, owner);
         if ( !res )
@@ -136,9 +140,8 @@ shadow_get_page_from_l1e(shadow_l1e_t sl
          * already have checked that we're supposed to have access, so
          * we can just grab a reference directly.
          */
-        mfn = shadow_l1e_get_mfn(sl1e);
-        if ( mfn_valid(mfn) )
-            res = get_page_from_l1e(sl1e, d, page_get_owner(mfn_to_page(mfn)));
+        if ( owner )
+            res = get_page_from_l1e(sl1e, d, owner);
     }
 
     if ( unlikely(res < 0) )



  parent reply	other threads:[~2021-04-23 10:53 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-22 10:55 [PATCH v3 0/2] VMX: apic access page handling adjustments Jan Beulich
2021-02-22 10:56 ` [PATCH v3 1/2][4.15] VMX: delay p2m insertion of APIC access page Jan Beulich
2021-02-22 11:25   ` Ian Jackson
2021-02-22 14:05     ` Jan Beulich
2021-02-22 17:17       ` Ian Jackson
2021-02-22 12:15   ` Roger Pau Monné
2021-02-25  8:44   ` Jan Beulich
2021-02-26  7:06     ` Tian, Kevin
2021-02-22 10:57 ` [PATCH v3 2/2] VMX: use a single, global " Jan Beulich
2021-03-01  2:34   ` Tian, Kevin
2021-03-01  8:18     ` Jan Beulich
2021-04-12 10:40 ` [PATCH v4] " Jan Beulich
2021-04-12 15:31   ` Roger Pau Monné
2021-04-13  9:24     ` Jan Beulich
2021-04-13 10:18       ` Roger Pau Monné
2021-04-13 12:03         ` Jan Beulich
2021-04-13 13:03           ` Roger Pau Monné
2021-04-17 19:24   ` Tim Deegan
2021-04-19 11:25     ` Jan Beulich
2021-04-22  7:42       ` Tim Deegan
2021-04-22  9:38         ` Jan Beulich
2021-04-22 15:05           ` Tim Deegan
2021-04-23 10:51 ` [PATCH v4 0/3] VMX APIC access page and shadow adjustments Jan Beulich
2021-04-23 10:52   ` [PATCH v4 1/3] VMX: use a single, global APIC access page Jan Beulich
2021-04-23 14:17     ` Roger Pau Monné
2021-04-23 14:42       ` Jan Beulich
2021-04-26 17:55         ` Tim Deegan
2021-04-25  1:27     ` Tian, Kevin
2021-04-26 17:53     ` Tim Deegan
2021-04-23 10:53   ` Jan Beulich [this message]
2021-04-23 10:54   ` [PATCH v4 3/3] x86/shadow: streamline shadow_get_page_from_l1e() Jan Beulich
2021-04-23 11:00   ` Really v5 (was: [PATCH v4 0/3] VMX APIC access page and shadow adjustments) Jan Beulich

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