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

[Paolo Bonzini]

On 30/03/2018 19:02, Roman Kagan wrote:
> 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

Queued, thanks.

Paolo

> 
> 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(-)
>