Re: [Xen-devel] dom0 pvops crash

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2010-02-02 at 10:23 +0000, Pasi Kärkkäinen wrote:
> On Mon, Jan 25, 2010 at 06:26:26PM +0000, Ian Campbell wrote:
> > On Mon, 2010-01-25 at 18:18 +0000, Ian Pratt wrote:
> > > > Here's the hacky fix from last summer:
> > > > http://lists.xensource.com/archives/html/xen-devel/2009-06/msg00519.html
> > > > 
> > > > On my testbox I can trigger that bug just by compiling a kernel in dom0.
> > > > 
> > > > CONFIG_HIGHPTE=n is stable for me, while CONFIG_HIGHPTE=y most probably
> > > > makes dom0 crash during a kernel compile.
> > > > 
> > > > (dom0 and Xen are 32bit PAE)
> > > 
> > > Even if it worked reliably, CONFIG_HIGHPTE performance would be
> > > miserable: It takes an operation that is always going to be slow on
> > > any virtualized system (updating PTEs), and pounds the cr*p out of
> > > it...
> > 
> > Unfortunately distros tend to enable it on native and with pvops there
> > is often no separate Xen kernel build where it can be disabled.
> > 
> 
> I just noticed the default Fedora 12 32bit PAE kernel has CONFIG_HIGHPTE=y.
> Running simple "make -j2 bzImage && make -j2 modules" in the guest crashes 
> the kernel.
> 
> Some kind of workaround should be made..

Can you try the patch from
<1264613173.16526.97718.camel@xxxxxxxxxxxxxxxxxxxxxx>? (earlier in this
thread).

It's a hack in the form given there but I'm planning to clean it up so
it would be useful to know if the basic concept is sound.

Ian.


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