Re: QEMU VM crashes when enabling KVM

[Wayne Li]

Dear David Gibson,

I know you are under no obligation to respond, but if it's possible for you to find the time to respond to my question, I would be extremely grateful.  My team at Boeing has been stuck trying to get KVM working for our project for the last few months.  A good explanation of why this isn't possible would be absolutely critical.

-Thanks, Wayne Li

On Thu, Dec 12, 2019 at 1:17 AM Paolo Bonzini <address@hidden> wrote:

On 12/12/19 02:59, Wayne Li wrote:
> We wrote a project that is created on top of the QEMU source code; it
> calls functions from the QEMU code.  I run the executable created by
> compiling that project/QEMU code.  Anyway, looking at the following
> documentation:
>
> https://www.kernel.org/doc/Documentation/powerpc/cpu_families.txt
>
> It looks like the PowerPC 7457 is Book3S and the PowerPC e6500 is
> BookE.  Is that why you think I require a Book3S KVM?  Exactly why do
> you feel this way?  Also would that mean my team would need to go and
> buy a board with a Book3S processor?

CCing the PPC maintainer.  There are aspects of BookE and Book3S that
are different and not really interchangeable in the privileged interface.

Paolo

> -Thanks!, Wayne Li
>
> From my understanding
>
> On Wed, Dec 11, 2019 at 7:16 PM Paolo Bonzini <address@hidden
> <mailto:address@hidden>> wrote:
>
>     On 11/12/19 22:23, Wayne Li wrote:
>     >
>     > Now I am fairly sure KVM is actually enabled on the system.  Finding
>     > that out was another story that spanned a couple of months.  But long
>     > story short, lsmod doesn't show that the KVM kernel module is
>     running. 
>     > But that's because KVM is built-in and it can't actually be built as a
>     > loadable kernel module in this particular system.
>     >
>     > So I'm not really sure what could be the problem.  Though I was
>     thinking
>     > if I understood the error better that might help?  Following the
>     code I
>     > see that the "Missing PVR setting capability." is called when a
>     variable
>     > called "cap_segstate" is 0:
>     >
>     > if (!cap_segstate) {
>     >             fprintf(stderr, "kvm error: missing PVR setting
>     capability\n");
>     >             return -ENOSYS;
>     > }
>     >
>     > And the cap_segstate variable is set by the following function:
>     >
>     > cap_segstate = kvm_check_extension(s, KVM_CAP_PPC_SEGSTATE);
>
>     You are not saying how you are running QEMU.  I think you are using a
>     CPU model that requires a Book3S KVM.
>
>     Paolo
>