Re: [PATCH v10 26/27] KVM: nVMX: Enable CET support for nested guest

From: "Yang, Weijiang" <weijiang.yang@intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: <pbonzini@redhat.com>, <dave.hansen@intel.com>, <x86@kernel.org>,
	<kvm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<peterz@infradead.org>, <chao.gao@intel.com>,
	<rick.p.edgecombe@intel.com>, <mlevitsk@redhat.com>,
	<john.allen@amd.com>
Subject: Re: [PATCH v10 26/27] KVM: nVMX: Enable CET support for nested guest
Date: Mon, 6 May 2024 17:25:44 +0800	[thread overview]
Message-ID: <071499ba-16b3-4c79-8b4b-95c03faf7493@intel.com> (raw)
In-Reply-To: <ZjLO8FsnJ7NgED0G@google.com>

On 5/2/2024 7:23 AM, Sean Christopherson wrote:
> On Sun, Feb 18, 2024, Yang Weijiang wrote:
>> @@ -2438,6 +2460,30 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct loaded_vmcs *vmcs0
>>   	}
>>   }
>>   
>> +static inline void cet_vmcs_fields_get(struct kvm_vcpu *vcpu, u64 *ssp,
>> +				       u64 *s_cet, u64 *ssp_tbl)
>> +{
>> +	if (guest_can_use(vcpu, X86_FEATURE_SHSTK)) {
>> +		*ssp = vmcs_readl(GUEST_SSP);
>> +		*s_cet = vmcs_readl(GUEST_S_CET);
>> +		*ssp_tbl = vmcs_readl(GUEST_INTR_SSP_TABLE);
>> +	} else if (guest_can_use(vcpu, X86_FEATURE_IBT)) {
>> +		*s_cet = vmcs_readl(GUEST_S_CET);
>> +	}
> Same comments about accessing S_CET, please do so in a dedicated path.

Will change it, thanks!

>
>> +}
>> +
>> +static inline void cet_vmcs_fields_put(struct kvm_vcpu *vcpu, u64 ssp,
>> +				       u64 s_cet, u64 ssp_tbl)
> This should probably use "set" instead of "put".  I can't think of a single case
> where KVM uses "put" to describe writing state, e.g. "put" is always used when
> putting a reference or unloading state.

Yes, "put" is not proper in this case, will change it.

>
>> +{
>> +	if (guest_can_use(vcpu, X86_FEATURE_SHSTK)) {
>> +		vmcs_writel(GUEST_SSP, ssp);
>> +		vmcs_writel(GUEST_S_CET, s_cet);
>> +		vmcs_writel(GUEST_INTR_SSP_TABLE, ssp_tbl);
>> +	} else if (guest_can_use(vcpu, X86_FEATURE_IBT)) {
>> +		vmcs_writel(GUEST_S_CET, s_cet);
>> +	}
> And here.

OK.