[xen staging] x86/time: introduce helper to fetch Xen wallclock when running as a guest

[patchbot@xxxxxxx]

commit 9f16d4e65342668a573e06b7517a4bc3ea8a65f2
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Mon Sep 9 13:41:16 2024 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Sep 9 13:41:16 2024 +0200

    x86/time: introduce helper to fetch Xen wallclock when running as a guest
    
    Move the current code in get_wallclock_time() to fetch the Xen wallclock
    information from the shared page when running as a guest into a separate
    helper.
    
    No functional change intended.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/time.c | 42 +++++++++++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index a97d784841..3c4cd1b595 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -787,6 +787,30 @@ static struct platform_timesource __initdata_cf_clobber 
plt_xen_timer =
 };
 #endif
 
+static unsigned long read_xen_wallclock(void)
+{
+#ifdef CONFIG_XEN_GUEST
+    const struct shared_info *sh_info = XEN_shared_info;
+    uint32_t wc_version;
+    uint64_t wc_sec;
+
+    ASSERT(xen_guest);
+
+    do {
+        wc_version = sh_info->wc_version & ~1;
+        smp_rmb();
+
+        wc_sec  = sh_info->wc_sec;
+        smp_rmb();
+    } while ( wc_version != sh_info->wc_version );
+
+    return wc_sec + read_xen_timer() / 1000000000;
+#else
+    ASSERT_UNREACHABLE();
+    return 0;
+#endif
+}
+
 #ifdef CONFIG_HYPERV_GUEST
 /************************************************************
  * HYPER-V REFERENCE TSC
@@ -1497,24 +1521,8 @@ void rtc_guest_write(unsigned int port, unsigned int 
data)
 
 static unsigned long get_wallclock_time(void)
 {
-#ifdef CONFIG_XEN_GUEST
     if ( xen_guest )
-    {
-        struct shared_info *sh_info = XEN_shared_info;
-        uint32_t wc_version;
-        uint64_t wc_sec;
-
-        do {
-            wc_version = sh_info->wc_version & ~1;
-            smp_rmb();
-
-            wc_sec  = sh_info->wc_sec;
-            smp_rmb();
-        } while ( wc_version != sh_info->wc_version );
-
-        return wc_sec + read_xen_timer() / 1000000000;
-    }
-#endif
+        return read_xen_wallclock();
 
     return get_cmos_time();
 }
--
generated by git-patchbot for /home/xen/git/xen.git#staging