[Qemu-devel] [PATCH for-2.12 v3 0/2] i386/hyperv: fully control Hyper-V features in CPUID

[Roman Kagan <rkagan@virtuozzo.com>]

In order to guarantee compatibility on migration, QEMU should have
complete control over the features it announces to the guest via CPUID.

However, a number of Hyper-V-related features happen to depend on the
support in the underlying KVM, with no regard to QEMU configuration.

Make QEMU regain control over what Hyper-V features it announces to the
guest.

Note #1: the patches are also being proposed[*] for stable-2.11, even
though one of them introduces a new cpu property.  This is done to
minimize the number of published QEMU releases where the behavior of the
features is unpredictable, with potentially fatal consequences for the
guest.

Note #2: there are other problems in the surrounding code, like ugly
error reporting or inconsistent population of MSRs.  I think this can be
put off to post-2.12.

[*] for the stable branch the second patch will have error returns
replaced with warnings; I'll post a separate series.

v2 -> v3:
 - include the fix for 'hv-time' missed previously

v1 -> v2:
 - indicate what flag requested the feature that can't be enabled in the
   error message
 - fix a typo in the error message for VP_RUNTIME

Roman Kagan (2):
  i386/hyperv: add hv-frequencies cpu property
  i386/hyperv: error out if features requested but unsupported

 target/i386/cpu.h |  1 +
 target/i386/cpu.c |  1 +
 target/i386/kvm.c | 56 ++++++++++++++++++++++++++++++++++++++++++-------------
 3 files changed, 45 insertions(+), 13 deletions(-)

-- 
2.14.3