linux-kernel - Re: [PATCH v9 22/27] KVM: VMX: Set up interception for CET MSRs

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Date: Fri, 26 Jan 2024 17:36:06 +0800
From: "Yang, Weijiang" <weijiang.yang@...el.com>
To: Chao Gao <chao.gao@...el.com>
CC: <seanjc@...gle.com>, <pbonzini@...hat.com>, <dave.hansen@...el.com>,
	<kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
	<yuan.yao@...ux.intel.com>, <peterz@...radead.org>,
	<rick.p.edgecombe@...el.com>, <mlevitsk@...hat.com>, <john.allen@....com>
Subject: Re: [PATCH v9 22/27] KVM: VMX: Set up interception for CET MSRs

On 1/26/2024 11:54 AM, Chao Gao wrote:
> On Tue, Jan 23, 2024 at 06:41:55PM -0800, Yang Weijiang wrote:
>> Enable/disable CET MSRs interception per associated feature configuration.
>> Shadow Stack feature requires all CET MSRs passed through to guest to make
>> it supported in user and supervisor mode while IBT feature only depends on
>> MSR_IA32_{U,S}_CETS_CET to enable user and supervisor IBT.
>>
>> Note, this MSR design introduced an architectural limitation of SHSTK and
>> IBT control for guest, i.e., when SHSTK is exposed, IBT is also available
>> to guest from architectual perspective since IBT relies on subset of SHSTK
>> relevant MSRs.
>>
>> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
>> Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
> Reviewed-by: Chao Gao <chao.gao@...el.com>
>
> one nit below,
>
>> ---
>> arch/x86/kvm/vmx/vmx.c | 41 +++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 41 insertions(+)
>>
>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>> index 064a5fe87948..34e91dbbffed 100644
>> --- a/arch/x86/kvm/vmx/vmx.c
>> +++ b/arch/x86/kvm/vmx/vmx.c
>> @@ -692,6 +692,10 @@ static bool is_valid_passthrough_msr(u32 msr)
>> 	case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 8:
>> 		/* LBR MSRs. These are handled in vmx_update_intercept_for_lbr_msrs() */
>> 		return true;
>> +	case MSR_IA32_U_CET:
>> +	case MSR_IA32_S_CET:
>> +	case MSR_IA32_PL0_SSP ... MSR_IA32_INT_SSP_TAB:
>> +		return true;
> Please update the comment above vmx_possible_passthrough_msrs[] to indicate CET
> MSRs are also handled separately.

OK, will do it, thanks!