Re: [PATCH 2/2] KVM: nVMX: invvpid handling improvements

["Radim Krčmář" <rkrcmar@redhat.com>]

2016-10-25 10:08+0200, Ladi Prosek:
> On Fri, Oct 21, 2016 at 10:02 PM, Radim Krčmář <rkrcmar@redhat.com> wrote:
>> 2016-10-19 01:45+0300, Jan Dakinevich:
>>>  - Expose all invalidation types to the L1
>>>
>>>  - Reject invvpid instruction, if L1 passed zero vpid value to single
>>>    context invalidations
>>>
>>> Signed-off-by: Jan Dakinevich <jan.dakinevich@gmail.com>
>>> ---
>>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>>> @@ -132,6 +132,11 @@
>>>
>>>  #define VMX_MISC_EMULATED_PREEMPTION_TIMER_RATE 5
>>>
>>> +#define VMX_VPID_EXTENT_ALL_MASK (VMX_VPID_EXTENT_INDIVIDUAL_ADDR_BIT |      \
>>
>> SUPPORTED instead of ALL would be a better name.
>>
>>> +     VMX_VPID_EXTENT_SINGLE_CONTEXT_BIT |                            \
>>> +     VMX_VPID_EXTENT_GLOBAL_CONTEXT_BIT |                            \
>>> +     VMX_VPID_EXTENT_SINGLE_CONTEXT_RETAINING_GLOBALS_BIT)
>>> +
>>>  /*
>>>   * These 2 parameters are used to config the controls for Pause-Loop Exiting:
>>>   * ple_gap:    upper bound on the amount of time between two successive
>>> @@ -2838,8 +2843,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
>>>        */
>>>       if (enable_vpid)
>>>               vmx->nested.nested_vmx_vpid_caps = VMX_VPID_INVVPID_BIT |
>>> -                             VMX_VPID_EXTENT_SINGLE_CONTEXT_BIT |
>>> -                             VMX_VPID_EXTENT_GLOBAL_CONTEXT_BIT;
>>> +                     VMX_VPID_EXTENT_ALL_MASK;
>>
>> I'd still support only type 2, because it is the only one we implement,
>> and type 1, because of buggy KVMs.
>>
>> Are there some OSes that can't use single or all context invalidation,
>> so supporting more might benefit something?
> 
> Windows Server 2016 with Hyper-V enabled requires all four
> invalidation types. The log message is not super clear, just
> s/allowed/required/ and s/required/available/

Yep, I would have understood it the other way around ...

> "
> Hypervisor launch failed;
> Processor does not support the minimum features required to run the hypervisor
> (MSR index 0x48C, allowed bits 0xF0106104040, required bits 0x60106114041).
> "
> 
> I have verified that adding VMX_VPID_EXTENT_INDIVIDUAL_ADDR and
> VMX_VPID_EXTENT_SINGLE_CONTEXT_RETAINING_GLOBALS solves this,

Great info.  Jan, I take back the conservativeness in review -- we'll
want to support the currently existing modes.  (Invalidating unnecessary
entries is sad, but not that bad ... nested is already slow.)

>                                                               although
> it's not the only issue preventing Hyper-V from running on KVM at the
> moment.

You mentioned another "allowed" bit that KVM lacks, which one was it?

Thanks.