Xen devel - May 2010 - Problem running latest Xen unstable hypervisor with latest Linux kernels

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.

Specifically I can boot up dom0 just fine.  When I try to start the guest Linux 
gets as far as "blkfront: xvdb1: barriers enabled", then hangs.  This
happens
with the xen/master branch as well as xen/core.  Returning to last
week''s
hypervisor lets me boot the guest just fine.

I assume I have some combination of config options set/not set that no longer 
works with the new hypervisor code.  Is there something simple I need to 
change?

Thanks,
Dave McCracken

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On 21/05/2010 14:55, "Dave McCracken" <dcm@mccr.org> 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.

 -- Keir
> Specifically I can boot up dom0 just fine.  When I try to start the guest
> Linux 
> gets as far as "blkfront: xvdb1: barriers enabled", then hangs. 
This happens
> with the xen/master branch as well as xen/core.  Returning to last
week''s
> hypervisor lets me boot the guest just fine.
> 
> I assume I have some combination of config options set/not set that no
longer
> works with the new hypervisor code.  Is there something simple I need to
> change?
> 
> Thanks,
> Dave McCracken


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On Fri, 21 May 2010, Keir Fraser wrote:
> On 21/05/2010 14:55, "Dave McCracken" <dcm@mccr.org> 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@eu.citrix.com>

---

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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On Fri, 21 May 2010, Stefano Stabellini wrote:
> On Fri, 21 May 2010, Keir Fraser wrote:
> > On 21/05/2010 14:55, "Dave McCracken" <dcm@mccr.org>
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:
> 
Oops, forgot the attachment



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On Friday, May 21, 2010, Keir Fraser 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.
The guest now boots just fine.  Thanks.

Dave

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