linux-kernel - Re: Nested KVM is broken on a AMD Ryzen 5 2400G

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Date:   Thu, 24 Jan 2019 17:11:18 -0200
From:   Diego Viola <diego.viola@...il.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     pbonzini@...hat.com, rkrcmar@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: Nested KVM is broken on a AMD Ryzen 5 2400G

Hi Joerg,

On Thu, Jan 24, 2019 at 6:42 AM Joerg Roedel <joro@...tes.org> wrote:
>
> Hi Diego,
>
> thanks for the report!

You're welcome, many thanks for your quick reply.

>
> On Thu, Jan 24, 2019 at 01:57:31AM -0200, Diego Viola wrote:
> > [10499.577192] WARNING: CPU: 2 PID: 3487 at arch/x86/kvm/mmu.c:2066
> > nonpaging_update_pte+0x5/0x10 [kvm]
>
> Seems like the nested-paging emulation got broken somewhere in the past.
> Can you try to load the KVM module in the guest with 'npt=0' and see if
> it works then?

I tried this and snapcraft is still timing out on the guest:

diego@...go-Standard-PC-i440FX-PIIX-1996:~/mysnaps/hello$ snapcraft
Launching a VM.
start failed: timed out waiting for instance to respond
Stopping snapcraft-my-snap-name /^C
Aborted!
diego@...go-Standard-PC-i440FX-PIIX-1996:~/mysnaps/hello$

That said, I no longer see the dmesg stack trace on the host. Should I
try a more recent kernel on the guest?

>
> Thanks,
>
>         Joerg

Regards,
Diego