[Xen-devel] Re: Problem running latest Xen unstable hypervisor with latest Linux kernels

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 21 May 2010, Keir Fraser wrote:
> On 21/05/2010 14:55, "Dave McCracken" <dcm@xxxxxxxx> wrote:
> 
> > I have a test box set up to run mainline Xen unstable hypervisor and a guest
> > running the latest Linux builds from Jeremy.  Last week it all worked fine.
> > This week when I pulled the latest unstable it stopped working.
> 
> This is a hypervisor bug. I would have bet that my recent smpboot/hotplug
> changes might have caused it, but happily I can report that I am not to
> blame. The offending changeset is 21339:804304d4e05d "x86: TSC handling
> cleanups" by Stefano (cc'ed). The automated regression tests have also been
> failing ever since it went in, so clearly PV guest startup failure is not
> hard to repro with this patch applied. For now I have reverted it
> (xen-unstable:21444), so please re-pull, re-build, re-test.
> 

Found the bug, I am attaching the full patch to the email, the following
is the diff to the previous version:

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

---

diff -r d84c1921e442 xen/arch/x86/time.c
--- a/xen/arch/x86/time.c       Fri May 21 17:11:21 2010 +0100
+++ b/xen/arch/x86/time.c       Fri May 21 17:28:59 2010 +0100
@@ -1636,7 +1636,6 @@
 {
     s_time_t now = get_s_time();
     struct domain *d = v->domain;
-    u64 tsc;
 
     spin_lock(&d->arch.vtsc_lock);
 
@@ -1652,7 +1651,7 @@
 
     spin_unlock(&d->arch.vtsc_lock);
 
-    tsc = gtime_to_gtsc(d, now);
+    now = gtime_to_gtsc(d, now);
 
     regs->eax = (uint32_t)now;
     regs->edx = (uint32_t)(now >> 32);

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