Re: Nested paging in nested SVM setup

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2014-06-18 13:36, Valentine Sinitsyn wrote:
> Hi all,
> 
> I'm using a KVM/Qemu nested SVM setup to debug another hypervisor
> (Jailhouse) I contribute to. IOW, the scheme is: AMD64 Linux host
> running [paravirtualized] AMD64 Linux guest (the same kernel as the
> host) running Jailhouse.
> 
> Jailhouse, in turn, uses Nested Paging to virtualize xAPIC: APIC page
> (0xfee00000, no APIC remapping) is mapped read-only into Jailhouse's
> guests. This of course implies that APIC page appears to Jailhouse
> guests as uncacheable (UC).
> 
> Is it achievable in the setup I described, or do I need to run my code
> on a real hardware to make the APIC page accesses in Jailhouse guests
> uncacheable?

If we want to provide useful nested SVM support, this must be feasible.
If there is a bug, it has to be fixed.

Maybe you can describe how you configured the involved units (NPT
structures, guest / host PAR, MTRR etc.).

Even better would be a test case based on kvm-unit-tests (see [1],
x86/svm.c) that replicates the observed behavior. If it reveals a bug,
this test would be very valuable for making sure it remains fixed (once
that is done).

Jan

[1] https://git.kernel.org/cgit/virt/kvm/kvm-unit-tests.git

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