> On 15 Apr 2016, at 10:15 PM, Tamas K Lengyel <tamas.leng...@zentific.com>
> wrote:
>
>
> On Apr 15, 2016 07:46, "liuweijie" <liuwj0...@163.com
> <mailto:liuwj0...@163.com>> wrote:
> >
> > Dear list,
> >
> > When I use VMFUNC instructions on a Xen HVM, domain crashes sometimes.
> >
> > My serial console shows like this:
> >
> > domain_crash called from p2m.c:2204
> > Domain 1 (vcpu#0) crashed on cpu#7
> > ……
> >
> > My testbed runs on Xen-4.6.0, and my CPU is Intel i7-4790. I can provide
> > more logs if needed.
> >
> > I know you guys have implemented helpful interfaces to manage alternative
> > P2Ms in version 4.6. Those ‘hvm_altp2m_op’ hypercalls are invoked before
> > VMFUNC instructions are executed. And ten alternative P2Ms can be built
> > successfully.
> >
> > The pseudo-code of my experiment is as follows:
> >
> > for (i = 0; i < 10; i++)
> > switch the current eptp to eptp[i];
> >
> >
> > However, once switching to eptp[4], namely when doing "mov eax 0; mov ecx
> > 4; vmfunc.”, my Ubuntu HVM crashes. And as soon as I switched to more than
> > 4 EPTPs, it crashed too. In other words, when I executed VMFUNC to switch
> > to the fifth different altp2m, the domain would crash.
> >
> > Then when I just created 4 altp2ms, that weird phenomenon never happened
> > again. Four altp2ms seems tolerable, but I still would like to use more. In
> > addition, the Intel manual says we can switch between 512 altp2ms, right?
> >
> > FYI, I know the bug lies in the function ‘p2m_altp2m_lazy_copy’, and it is
> > caused by the wrong return number of function ‘p2m_set_entry’.
> >
> > Can you guys fix the bug? Or is there something wrong with my test?
> >
> > Any help is appreciated! Thanks so much!
> >
> > Cheers,
> > Weijie.
>
> Hi Weijie,
> While the hardware could handle 512 EPTs Xen only implements support for up
> to 10. The crash you are seeing is likely caused by the domain running out
> hap pool space when trying to copy the EPT to the new table. Try adding
> 'shadow_memory=16' to your domain config, it should fix the crash.
>
> Cheers,
>
> Tamas
Thanks so much, Tamas!! Now it is working!
I knew DRAKVUF! Big fan! So excited!
Weijie.
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