Re: [PATCH] KVM: nVMX: Don't expose TSC scaling to L1 when on Hyper-V

[Vitaly Kuznetsov]

Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> writes:

> Anirudh Rayabharam <anrayabh@xxxxxxxxxxxxxxxxxxx> writes:
>
> ...
>
>>
>> As per the comments in arch/x86/kvm/vmx/evmcs.h, TSC multiplier field is
>> currently not supported in EVMCS.
>
> The latest version:
> https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/datatypes/hv_vmx_enlightened_vmcs
>
> has it, actually. It was missing before (compare with e.g. 6.0b version
> here:
> https://github.com/MicrosoftDocs/Virtualization-Documentation/raw/live/tlfs/Hypervisor%20Top%20Level%20Functional%20Specification%20v6.0b.pdf)
>
> but AFAIR TSC scaling wasn't advertised by genuine Hyper-V either.
> Interestingly enough, eVMCS version didn't change when these fields were
> added, it is still '1'.
>
> I even have a patch in my stash (attached). I didn't send it out because
> it wasn't properly tested with different Hyper-V versions.

And of course I forgot a pre-requisite patch which updates 'struct
hv_enlightened_vmcs' to the latest:

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 0a9407dc0859..038e5ef9b4a6 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -559,9 +559,20 @@ struct hv_enlightened_vmcs {
        u64 partition_assist_page;
        u64 padding64_4[4];
        u64 guest_bndcfgs;
-       u64 padding64_5[7];
+       u64 guest_ia32_perf_global_ctrl;
+       u64 guest_ia32_s_cet;
+       u64 guest_ssp;
+       u64 guest_ia32_int_ssp_table_addr;
+       u64 guest_ia32_lbr_ctl;
+       u64 padding64_5[2];
        u64 xss_exit_bitmap;
-       u64 padding64_6[7];
+       u64 host_ia32_perf_global_ctrl;
+       u64 encls_exiting_bitmap;
+       u64 tsc_multiplier;
+       u64 host_ia32_s_cet;
+       u64 host_ssp;
+       u64 host_ia32_int_ssp_table_addr;
+       u64 padding64_6;
 } __packed;
 
 #define HV_VMX_ENLIGHTENED_CLEAN_FIELD_NONE                    0

-- 
Vitaly