linux-kernel - Re: [PATCH v3 03/25] x86/hyperv: Update 'struct hv_enlightened

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Message-ID: <874jzmplqd.fsf@redhat.com>
Date:   Tue, 12 Jul 2022 14:19:06 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH v3 03/25] x86/hyperv: Update 'struct
 hv_enlightened_vmcs' definition

Maxim Levitsky <mlevitsk@...hat.com> writes:

> On Fri, 2022-07-08 at 16:42 +0200, Vitaly Kuznetsov wrote:
>> Updated Hyper-V Enlightened VMCS specification lists several new
>> fields for the following features:
>> 
>> - PerfGlobalCtrl
>> - EnclsExitingBitmap
>> - Tsc Scaling
>> - GuestLbrCtl
>> - CET
>> - SSP
>> 
>> Update the definition. The updated definition is available only when
>> CPUID.0x4000000A.EBX BIT(0) is '1'. Add a define for it as well.
>> 
>> Note: The latest TLFS is available at
>> https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/tlfs
>> 
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
>> ---
>>  arch/x86/include/asm/hyperv-tlfs.h | 18 ++++++++++++++++--
>>  1 file changed, 16 insertions(+), 2 deletions(-)
>> 
>> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
>> index 6f0acc45e67a..6f2c3cdacdf4 100644
>> --- a/arch/x86/include/asm/hyperv-tlfs.h
>> +++ b/arch/x86/include/asm/hyperv-tlfs.h
>> @@ -138,6 +138,9 @@
>>  #define HV_X64_NESTED_GUEST_MAPPING_FLUSH		BIT(18)
>>  #define HV_X64_NESTED_MSR_BITMAP			BIT(19)
>>  
>
> Maybe add a comment that this is undocumented + what that cpuid bit does?
>
>> +/* Nested quirks. These are HYPERV_CPUID_NESTED_FEATURES.EBX bits. */
>> +#define HV_X64_NESTED_EVMCS1_2022_UPDATE		BIT(0)
>> +
>>  /*
>>   * This is specific to AMD and specifies that enlightened TLB flush is
>>   * supported. If guest opts in to this feature, ASID invalidations only
>> @@ -559,9 +562,20 @@ 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];
>
> This change looks OK
>
>>  	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;
>
> I think we have a mistake here:
>
> UINT64 XssExitingBitmap;
> UINT64 EnclsExitingBitmap;
> UINT64 HostPerfGlobalCtrl;
> UINT64 TscMultiplier;
> UINT64 HostSCet;
> UINT64 HostSsp;
> UINT64 HostInterruptSspTableAddr;
> UINT64 Rsvd8;
>
>
> I think you need to swap encls_exiting_bitmap and host_ia32_perf_global_ctrl
>
> I used https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/datatypes/hv_vmx_enlightened_vmcs
> as the reference. 

Oh, nice catch, thanks! I have no idea how this mistake crept in. A
conspiracy theory: maybe the online version of TLFS was updated
under our feet? :-)

v4 is coming to rescue.

>
>
> Best regards,
> 	Maxim Levitsky
>
>
>>  } __packed;
>>  
>>  #define HV_VMX_ENLIGHTENED_CLEAN_FIELD_NONE			0
>
>

-- 
Vitaly