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X-CSE-ConnectionGUID: BkOlbauiTQu1sR+PwG3jTw== X-CSE-MsgGUID: LiCmhFnjSSmahkTYIUiiGA== X-IronPort-AV: E=McAfee;i="6700,10204,11309"; a="36534560" X-IronPort-AV: E=Sophos;i="6.12,300,1728975600"; d="scan'208";a="36534560" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by fmvoesa111.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jan 2025 18:09:32 -0800 X-CSE-ConnectionGUID: iQayFmnMSYa3iQY7BOCIEA== X-CSE-MsgGUID: lNxZgZsaRpKBrDG7fVaCLQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="104141748" Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.124.247.1]) ([10.124.247.1]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jan 2025 18:09:27 -0800 Message-ID: <95716dee-c929-4ccf-b312-8a94e4276ddb@intel.com> Date: Thu, 9 Jan 2025 10:09:24 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 11/16] KVM: TDX: Always block INIT/SIPI To: Sean Christopherson , Binbin Wu Cc: pbonzini@redhat.com, kvm@vger.kernel.org, rick.p.edgecombe@intel.com, kai.huang@intel.com, adrian.hunter@intel.com, reinette.chatre@intel.com, tony.lindgren@linux.intel.com, isaku.yamahata@intel.com, yan.y.zhao@intel.com, chao.gao@intel.com, linux-kernel@vger.kernel.org References: <20241209010734.3543481-1-binbin.wu@linux.intel.com> <20241209010734.3543481-12-binbin.wu@linux.intel.com> <473c1a20-11c8-4e4e-8ff1-e2e5c5d68332@intel.com> <904c0aa7-8aa6-4ac2-b2d3-9bac89355af1@linux.intel.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 1/8/2025 10:40 PM, Sean Christopherson wrote: > On Wed, Jan 08, 2025, Binbin Wu wrote: >> On 1/8/2025 3:21 PM, Xiaoyao Li wrote: >>> On 12/9/2024 9:07 AM, Binbin Wu wrote: > > ... > >>>> --- >>>>   arch/x86/kvm/lapic.c    |  2 +- >>>>   arch/x86/kvm/vmx/main.c | 19 ++++++++++++++++++- >>>>   2 files changed, 19 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c >>>> index 474e0a7c1069..f93c382344ee 100644 >>>> --- a/arch/x86/kvm/lapic.c >>>> +++ b/arch/x86/kvm/lapic.c >>>> @@ -3365,7 +3365,7 @@ int kvm_apic_accept_events(struct kvm_vcpu *vcpu) >>>>         if (test_and_clear_bit(KVM_APIC_INIT, &apic->pending_events)) { >>>>           kvm_vcpu_reset(vcpu, true); >>>> -        if (kvm_vcpu_is_bsp(apic->vcpu)) >>>> +        if (kvm_vcpu_is_bsp(vcpu)) >>>>               vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE; >>>>           else >>>>               vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED; >>>> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c >>>> index 8ec96646faec..7f933f821188 100644 >>>> --- a/arch/x86/kvm/vmx/main.c >>>> +++ b/arch/x86/kvm/vmx/main.c >>>> @@ -115,6 +115,11 @@ static void vt_vcpu_free(struct kvm_vcpu *vcpu) >>>>     static void vt_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) >>>>   { >>>> +    /* >>>> +     * TDX has its own sequence to do init during TD build time (by >>>> +     * KVM_TDX_INIT_VCPU) and it doesn't support INIT event during TD >>>> +     * runtime. >>>> +     */ >>> >>> The first half is confusing. It seems to mix up init(ialization) with INIT >>> event. >>> >>> And this callback is about *reset*, which can be due to INIT event or not. >>> That's why it has a second parameter of init_event. The comment needs to >>> clarify why reset is not needed for both cases. >>> >>> I think we can just say TDX doesn't support vcpu reset no matter due to >>> INIT event or not. > > That's not entirely accurate either though. TDX does support KVM's version of > RESET, because KVM's RESET is "power-on", i.e. vCPU creation. Emulation of > runtime RESET is userspace's responsibility. > > The real reason why KVM doesn't do anything during KVM's RESET is that what > little setup KVM does/can do needs to be defered until after guest CPUID is > configured. It's much clear now. > KVM should also WARN if a TDX vCPU gets INIT, no? Agreed. > Side topic, the comment about x2APIC in tdx_vcpu_init() is too specific, e.g. > calling out that x2APIC support is enumerated in CPUID.0x1.ECX isn't necessary, > and stating that userspace must use KVM_SET_CPUID2 is flat out wrong. Very > technically, KVM_SET_CPUID is also a valid option, it's just not used in practice > because it doesn't support setting non-zero indices (but in theory it could be > used to enable x2APIC). > > E.g. something like this? LGTM. > diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c > index d2e78e6675b9..e36fba94fa14 100644 > --- a/arch/x86/kvm/vmx/main.c > +++ b/arch/x86/kvm/vmx/main.c > @@ -115,13 +115,10 @@ static void vt_vcpu_free(struct kvm_vcpu *vcpu) > > static void vt_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) > { > - /* > - * TDX has its own sequence to do init during TD build time (by > - * KVM_TDX_INIT_VCPU) and it doesn't support INIT event during TD > - * runtime. > - */ > - if (is_td_vcpu(vcpu)) > + if (is_td_vcpu(vcpu)) { > + tdx_vcpu_reset(vcpu, init_event); > return; > + } > > vmx_vcpu_reset(vcpu, init_event); > } > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c > index 9e490fccf073..a587f59167a7 100644 > --- a/arch/x86/kvm/vmx/tdx.c > +++ b/arch/x86/kvm/vmx/tdx.c > @@ -2806,9 +2806,8 @@ static int tdx_vcpu_init(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *cmd) > return -EINVAL; > > /* > - * As TDX requires X2APIC, set local apic mode to X2APIC. User space > - * VMM, e.g. qemu, is required to set CPUID[0x1].ecx.X2APIC=1 by > - * KVM_SET_CPUID2. Otherwise kvm_apic_set_base() will fail. > + * TDX requires x2APIC, userspace is responsible for configuring guest > + * CPUID accordingly. > */ > apic_base = APIC_DEFAULT_PHYS_BASE | LAPIC_MODE_X2APIC | > (kvm_vcpu_is_reset_bsp(vcpu) ? MSR_IA32_APICBASE_BSP : 0); > @@ -2827,6 +2826,19 @@ static int tdx_vcpu_init(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *cmd) > return 0; > } > > +void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) > +{ > + /* > + * Yell on INIT, as TDX doesn't support INIT, i.e. KVM should drop all > + * INIT events. > + * > + * Defer initializing vCPU for RESET state until KVM_TDX_INIT_VCPU, as > + * userspace needs to define the vCPU model before KVM can initialize > + * vCPU state, e.g. to enable x2APIC. > + */ > + WARN_ON_ONCE(init_event); > +} > + > struct tdx_gmem_post_populate_arg { > struct kvm_vcpu *vcpu; > __u32 flags; >