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

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Date:   Tue, 12 Jul 2022 14:51:09 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
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
Subject: Re: [PATCH v3 03/25] x86/hyperv: Update 'struct
 hv_enlightened_vmcs' definition

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. 


Best regards,
	Maxim Levitsky


>  } __packed;
>  
>  #define HV_VMX_ENLIGHTENED_CLEAN_FIELD_NONE			0