On Thu, Aug 18, 2022, Vitaly Kuznetsov wrote:

Sean Christopherson [off-list ref] writes:

quoted

On Tue, Aug 02, 2022, Vitaly Kuznetsov wrote:

quoted

For some features, Hyper-V spec defines two separate CPUID bits: one
listing whether the feature is supported or not and another one showing
whether guest partition was granted access to the feature ("partition
privilege mask"). 'Debug MSRs available' is one of such features. Add
the missing 'access' bit.

Note: hv_check_msr_access() deliberately keeps checking
HV_FEATURE_DEBUG_MSRS_AVAILABLE bit instead of the new HV_ACCESS_DEBUG_MSRS
to not break existing VMMs (QEMU) which only expose one bit. Normally, VMMs
should set either both these bits or none.

This is not the right approach long term.  If KVM absolutely cannot unconditionally
switch to checking HV_ACCESS_DEBUG_MSRS because it would break QEMU users, then we
should add a quirk, but sweeping the whole thing under the rug is wrong.

First, this patch is kind of unrelated to the series so in case it's the
only thing which blocks it from being merged -- let's just pull it out
and discuss separately.

Regarding the series, are there any true dependencies between the eVMCS patches
(1 - 11) and the VMCS sanitization rework (12 - 26)?  I.e. can the VMCS rework
be queued ahead of the eVMCS v1 support?