From: Chris Lalancette <clalance@redhat.com>
Date: Mon, 10 Dec 2007 09:54:11 -0500
Subject: [xen] x86: suppress bogus timer warning
Message-id: 475D5313.5020703@redhat.com
O-Subject: [RHEL5.2 PATCH]: Suppress bogus timer warning
Bugzilla: 317201

All,
     Attached is a fairly simple patch to fix BZ 317201.  Basically, when
running a 2.6.23 or newer kernel in an HVM guest, the hypervisor would
continually spit out:

(XEN) vpt.c:210:d3 HVM_PlatformTime: program too small period 192480

This happens because of the tickless stuff that continually reprograms the
APIC's; the HV, of course, is emulating the APIC's, and spits this message if
the period for the timer is less than 0.9ms.  However, that logic really should
only apply to periodic timers, not one-shot.  This patch adds a check to make
sure it is periodic before printing out the messages.

This is from upstream xen-3.1-testing.hg c/s 15504.

Successfully tested by me; before the patch, I would get constant spew, and
after the patch the messages were suppressed.

Please ACK.

Chris Lalancette

# HG changeset patch
# User Keir Fraser <keir.fraser@citrix.com>
# Date 1196957712 0
# Node ID cbac6d0a78fd17e2729ca3a827c0d5022afec18f
# Parent  912279dd383616d6031b7f646a3f5e47c76e02d9
hvm: Only complain about short-period periodic tickers.
Signed-off-by: Keir Fraser <keir@xensource.com>
xen-unstable changeset:   15610:ad1c6cf0baafe149c9fe03be3255b95ffef68a34
xen-unstable date:        Wed Jul 18 11:00:32 2007 +0100

Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Acked-by: "Stephen C. Tweedie" <sct@redhat.com>

diff --git a/arch/x86/hvm/vpt.c b/arch/x86/hvm/vpt.c
index cbd1ffa..5ea7303 100644
--- a/arch/x86/hvm/vpt.c
+++ b/arch/x86/hvm/vpt.c
@@ -260,13 +260,15 @@ void create_periodic_time(
     pt->enabled = 1;
     pt->pending_intr_nr = 0;
 
-    if ( period < 900000 ) /* < 0.9 ms */
+    /* Periodic timer must be at least 0.9ms. */
+    if ( (period < 900000) && !one_shot )
     {
         gdprintk(XENLOG_WARNING,
                  "HVM_PlatformTime: program too small period %"PRIu64"\n",
                  period);
-        period = 900000; /* force to 0.9ms */
+        period = 900000;
     }
+
     pt->period = period;
     pt->vcpu = v;
     pt->last_plt_gtime = hvm_get_guest_time(pt->vcpu);