Re: [Qemu-devel] [PATCH] hw/arm/virt: smbios: inform guest of kvm

[Andrew Jones <drjones@redhat.com>]

On Wed, Sep 23, 2015 at 08:43:39AM -0700, Peter Maydell wrote:
> On 23 September 2015 at 07:18, Andrew Jones <drjones@redhat.com> wrote:
> > ARM/AArch64 KVM guests don't have any way to identify
> > themselves as KVM guests (x86 guests use a CPUID leaf). Now, we
> > could discuss all sorts of reasons why guests shouldn't need to
> > know that, but then there's always some case where it'd be
> > nice... Anyway, now that we have SMBIOS tables in ARM guests,
> > it's easy for the guest to know that it's a QEMU instance. This
> > patch takes that one step further, also identifying KVM, when
> > appropriate. Again, we could debate why generally nothing
> > should care whether it's of type QEMU or QEMU/KVM, but again,
> > sometimes it's nice to know...
> 
> This doesn't seem great to me, because it's ACPI/SMBIOS
> specific. A mechanism that worked whether the guest was
> booted via APCI or DT would seem preferable to me...

SMBIOS is populated on both ACPI and devicetree boots. We already
have detection in virt-what and systemd-detect-virt for DT boots,
although it only detects QEMU (it can't determine if KVM is used).
That detection is DT-specific, and much more of a heuristic, it
checks for the presence of the fw-cfg node in the DT. Actually, I'd
like to patch those virt detection tools to try SMBIOS first (which,
with this patch, could also give KVM info), and then fall back to
trying the current DT-only, QEMU-only detection, before giving up.

Thanks,
drew