linux-kernel - Re: [PATCH v9 19/22] KVM: nVMX: Handle FRED VMCS fields in nested VMX context

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Message-ID: <aTdTIWND0d_pyefu@google.com>
Date: Mon, 8 Dec 2025 14:37:21 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: "Xin Li (Intel)" <xin@...or.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	linux-doc@...r.kernel.org, pbonzini@...hat.com, corbet@....net, 
	tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, 
	dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com, luto@...nel.org, 
	peterz@...radead.org, andrew.cooper3@...rix.com, chao.gao@...el.com, 
	hch@...radead.org, sohil.mehta@...el.com
Subject: Re: [PATCH v9 19/22] KVM: nVMX: Handle FRED VMCS fields in nested VMX context

On Sun, Oct 26, 2025, Xin Li (Intel) wrote:
> diff --git a/arch/x86/kvm/vmx/vmcs_shadow_fields.h b/arch/x86/kvm/vmx/vmcs_shadow_fields.h
> index cad128d1657b..da338327c2b3 100644
> --- a/arch/x86/kvm/vmx/vmcs_shadow_fields.h
> +++ b/arch/x86/kvm/vmx/vmcs_shadow_fields.h
> @@ -74,6 +74,10 @@ SHADOW_FIELD_RW(HOST_GS_BASE, host_gs_base)
>  /* 64-bit */
>  SHADOW_FIELD_RO(GUEST_PHYSICAL_ADDRESS, guest_physical_address)
>  SHADOW_FIELD_RO(GUEST_PHYSICAL_ADDRESS_HIGH, guest_physical_address)
> +SHADOW_FIELD_RO(ORIGINAL_EVENT_DATA, original_event_data)
> +SHADOW_FIELD_RO(ORIGINAL_EVENT_DATA_HIGH, original_event_data)
> +SHADOW_FIELD_RW(INJECTED_EVENT_DATA, injected_event_data)
> +SHADOW_FIELD_RW(INJECTED_EVENT_DATA_HIGH, injected_event_data)

Please add shadow fields in a separate patch, with sufficient explain to justify
why KVM needs to enable VMCS shadowing for the fields (it's purely a performance
optimazation).