Maxim Levitsky <mlevitsk@xxxxxxxxxx> writes:
> On Tue, 2022-02-08 at 16:15 +0100, Vitaly Kuznetsov wrote:
>>
>> "hv-vapic" enables so-called "VP Assist" page and Enlightened VMCS GPA
>> sits there, it is used instead of VMPTRLD (which becomes unsupported)
>>
>> Take a look at the newly introduced "hv-apicv"/"hv-avic" (the same
>> thing) in QEMU:
>>
>> commit e1f9a8e8c90ae54387922e33e5ac4fd759747d01
>> Author: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
>> Date: Thu Sep 2 11:35:28 2021 +0200
>>
>> i386: Implement pseudo 'hv-avic' ('hv-apicv') enlightenment
>>
>> when enabled, HV_APIC_ACCESS_RECOMMENDED is not set even with "hv-vapic"
>> (but HV_APIC_ACCESS_AVAILABLE remains).
>>
>
> Cool, I didn't expect this. I thought that hv-vapic only enables the AutoEOI
> deprecation bit.
>
> This needs to be updated in hyperv.txt in qemu - it currently states that
> hv-evmcs disables posted interrupts (that is APICv)
EVMCS disables (not only) posted interrupts feature for nested
guests. To be precise, it disables the following:
#define EVMCS1_UNSUPPORTED_PINCTRL (PIN_BASED_POSTED_INTR | \
PIN_BASED_VMX_PREEMPTION_TIMER)
#define EVMCS1_UNSUPPORTED_2NDEXEC \
(SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY | \
SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES | \
SECONDARY_EXEC_APIC_REGISTER_VIRT | \
SECONDARY_EXEC_ENABLE_PML | \
SECONDARY_EXEC_ENABLE_VMFUNC | \
SECONDARY_EXEC_SHADOW_VMCS | \
SECONDARY_EXEC_TSC_SCALING | \
SECONDARY_EXEC_PAUSE_LOOP_EXITING)
#define EVMCS1_UNSUPPORTED_VMEXIT_CTRL \
(VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL | \
VM_EXIT_SAVE_VMX_PREEMPTION_TIMER)
#define EVMCS1_UNSUPPORTED_VMENTRY_CTRL (VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL)
#define EVMCS1_UNSUPPORTED_VMFUNC (VMX_VMFUNC_EPTP_SWITCHING)
> and hv-avic only mentions AutoEOI feature.
True, this is hidden in "The enlightenment allows to use Hyper-V SynIC
with hardware APICv/AVIC enabled". Any suggestions on how to improve
this are more than welcome!.
--
Vitaly
