linux-kernel - Re: [PATCH v15 14/14] KVM: x86: Save/Restore GUEST

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Date:   Wed, 3 Feb 2021 13:07:53 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yang Weijiang <weijiang.yang@...el.com>, seanjc@...gle.com,
        jmattson@...gle.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     yu.c.zhang@...ux.intel.com
Subject: Re: [PATCH v15 14/14] KVM: x86: Save/Restore GUEST_SSP to/from SMRAM

On 03/02/21 12:34, Yang Weijiang wrote:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 22eb6b8626a8..f63b713cd71f 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8592,6 +8592,16 @@ static void enter_smm_save_state_64(struct kvm_vcpu *vcpu, char *buf)
>   
>   	for (i = 0; i < 6; i++)
>   		enter_smm_save_seg_64(vcpu, buf, i);
> +
> +	if (kvm_cet_supported()) {
> +		struct msr_data msr;
> +
> +		msr.index = MSR_KVM_GUEST_SSP;
> +		msr.host_initiated = true;
> +		/* GUEST_SSP is stored in VMCS at vm-exit. */
> +		kvm_x86_ops.get_msr(vcpu, &msr);
> +		put_smstate(u64, buf, 0x7ec8, msr.data);
> +	}
>   }
>   #endif
>   
> 

0x7ec8 is used for I/O instruction restart and auto-halt restart. 
0x7f08 is a free spot.  We should really document the KVM state save 
area format.

Paolo