From: Sean Christopherson <seanjc@google.com>
To: Maxim Levitsky <mlevitsk@redhat.com>
Cc: Yang Weijiang <weijiang.yang@intel.com>,
pbonzini@redhat.com, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, dave.hansen@intel.com,
peterz@infradead.org, chao.gao@intel.com,
rick.p.edgecombe@intel.com, john.allen@amd.com
Subject: Re: [PATCH v6 23/25] KVM: x86: Enable CET virtualization for VMX and advertise to userspace
Date: Wed, 1 Nov 2023 15:14:58 -0700 [thread overview]
Message-ID: <ZULN4vMwP1t_mKg7@google.com> (raw)
In-Reply-To: <c07416ff2919f0aa30d3a810ccdfbed8c387ce0a.camel@redhat.com>
On Tue, Oct 31, 2023, Maxim Levitsky wrote:
> On Thu, 2023-09-14 at 02:33 -0400, Yang Weijiang wrote:
> > @@ -685,6 +686,13 @@ void kvm_set_cpu_caps(void)
> > kvm_cpu_cap_set(X86_FEATURE_INTEL_STIBP);
> > if (boot_cpu_has(X86_FEATURE_AMD_SSBD))
> > kvm_cpu_cap_set(X86_FEATURE_SPEC_CTRL_SSBD);
> > + /*
> > + * The feature bit in boot_cpu_data.x86_capability could have been
> > + * cleared due to ibt=off cmdline option, then add it back if CPU
> > + * supports IBT.
> > + */
> > + if (cpuid_edx(7) & F(IBT))
> > + kvm_cpu_cap_set(X86_FEATURE_IBT);
>
> The usual policy is that when the host doesn't support a feature, then the guest
> should not support it either. On the other hand, for this particular feature,
> it is probably safe to use it. Just a point for a discussion.
Agreed, this needs extra justification. It's "safe" in theory, but if the admin
disabled IBT because of a ucode bug, then all bets are off.
I'm guessing this was added because of the virtualization hole? I.e. if KVM
allows CR4.CET=1 for shadow stacks, then KVM can't (easily?) prevent the guest
from also using IBT.
next prev parent reply other threads:[~2023-11-01 22:15 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-14 6:33 [PATCH v6 00/25] Enable CET Virtualization Yang Weijiang
2023-09-14 6:33 ` [PATCH v6 01/25] x86/fpu/xstate: Manually check and add XFEATURE_CET_USER xstate bit Yang Weijiang
2023-09-14 22:39 ` Edgecombe, Rick P
2023-09-15 2:32 ` Yang, Weijiang
2023-09-15 16:35 ` Edgecombe, Rick P
2023-09-18 7:16 ` Yang, Weijiang
2023-10-31 17:43 ` Maxim Levitsky
2023-11-01 9:19 ` Yang, Weijiang
2023-09-14 6:33 ` [PATCH v6 02/25] x86/fpu/xstate: Fix guest fpstate allocation size calculation Yang Weijiang
2023-09-14 22:45 ` Edgecombe, Rick P
2023-09-15 2:45 ` Yang, Weijiang
2023-09-15 16:35 ` Edgecombe, Rick P
2023-10-21 0:39 ` Sean Christopherson
2023-10-24 8:50 ` Yang, Weijiang
2023-10-24 16:32 ` Sean Christopherson
2023-10-25 13:49 ` Yang, Weijiang
2023-10-31 17:43 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 03/25] x86/fpu/xstate: Add CET supervisor mode state support Yang Weijiang
2023-09-15 0:06 ` Edgecombe, Rick P
2023-09-15 6:30 ` Yang, Weijiang
2023-10-31 17:44 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 04/25] x86/fpu/xstate: Introduce kernel dynamic xfeature set Yang Weijiang
2023-09-15 0:24 ` Edgecombe, Rick P
2023-09-15 6:42 ` Yang, Weijiang
2023-10-31 17:44 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 05/25] x86/fpu/xstate: Remove kernel dynamic xfeatures from kernel default_features Yang Weijiang
2023-09-14 16:22 ` Dave Hansen
2023-09-15 1:52 ` Yang, Weijiang
2023-10-31 17:44 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 06/25] x86/fpu/xstate: Opt-in kernel dynamic bits when calculate guest xstate size Yang Weijiang
2023-09-14 17:40 ` Dave Hansen
2023-09-15 2:22 ` Yang, Weijiang
2023-10-24 17:07 ` Sean Christopherson
2023-10-25 14:49 ` Yang, Weijiang
2023-10-26 17:24 ` Sean Christopherson
2023-10-26 22:06 ` Edgecombe, Rick P
2023-10-31 17:45 ` Maxim Levitsky
2023-11-01 14:16 ` Sean Christopherson
2023-11-02 18:20 ` Maxim Levitsky
2023-11-03 14:33 ` Sean Christopherson
2023-11-07 18:04 ` Maxim Levitsky
2023-11-14 9:13 ` Yang, Weijiang
2023-09-14 6:33 ` [PATCH v6 07/25] x86/fpu/xstate: Tweak guest fpstate to support kernel dynamic xfeatures Yang Weijiang
2023-10-31 17:45 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 08/25] x86/fpu/xstate: WARN if normal fpstate contains " Yang Weijiang
2023-10-31 17:45 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 09/25] KVM: x86: Rework cpuid_get_supported_xcr0() to operate on vCPU data Yang Weijiang
2023-10-31 17:46 ` Maxim Levitsky
2023-11-01 14:41 ` Sean Christopherson
2023-11-02 18:25 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 10/25] KVM: x86: Add kvm_msr_{read,write}() helpers Yang Weijiang
2023-10-31 17:47 ` Maxim Levitsky
2023-11-01 19:32 ` Sean Christopherson
2023-11-02 18:26 ` Maxim Levitsky
2023-11-15 9:00 ` Yang, Weijiang
2023-09-14 6:33 ` [PATCH v6 11/25] KVM: x86: Report XSS as to-be-saved if there are supported features Yang Weijiang
2023-10-31 17:47 ` Maxim Levitsky
2023-11-01 19:18 ` Sean Christopherson
2023-11-02 18:31 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 12/25] KVM: x86: Refresh CPUID on write to guest MSR_IA32_XSS Yang Weijiang
2023-10-08 5:54 ` Chao Gao
2023-10-10 0:49 ` Yang, Weijiang
2023-10-31 17:51 ` Maxim Levitsky
2023-11-01 17:20 ` Sean Christopherson
2023-11-15 7:18 ` Binbin Wu
2023-09-14 6:33 ` [PATCH v6 13/25] KVM: x86: Initialize kvm_caps.supported_xss Yang Weijiang
2023-10-31 17:51 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 14/25] KVM: x86: Load guest FPU state when access XSAVE-managed MSRs Yang Weijiang
2023-10-31 17:51 ` Maxim Levitsky
2023-11-01 18:05 ` Sean Christopherson
2023-11-02 18:31 ` Maxim Levitsky
2023-11-03 8:46 ` Yang, Weijiang
2023-11-03 14:02 ` Sean Christopherson
2023-09-14 6:33 ` [PATCH v6 15/25] KVM: x86: Add fault checks for guest CR4.CET setting Yang Weijiang
2023-10-31 17:51 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 16/25] KVM: x86: Report KVM supported CET MSRs as to-be-saved Yang Weijiang
2023-10-08 6:19 ` Chao Gao
2023-10-10 0:54 ` Yang, Weijiang
2023-10-31 17:52 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 17/25] KVM: VMX: Introduce CET VMCS fields and control bits Yang Weijiang
2023-10-31 17:52 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 18/25] KVM: x86: Use KVM-governed feature framework to track "SHSTK/IBT enabled" Yang Weijiang
2023-10-31 17:54 ` Maxim Levitsky
2023-11-01 15:46 ` Sean Christopherson
2023-11-02 18:35 ` Maxim Levitsky
2023-11-04 0:07 ` Sean Christopherson
2023-11-07 18:05 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 19/25] KVM: VMX: Emulate read and write to CET MSRs Yang Weijiang
2023-10-31 17:55 ` Maxim Levitsky
2023-11-01 16:31 ` Sean Christopherson
2023-11-02 18:38 ` Maxim Levitsky
2023-11-02 23:58 ` Sean Christopherson
2023-11-07 18:12 ` Maxim Levitsky
2023-11-07 18:39 ` Sean Christopherson
2023-11-03 8:18 ` Yang, Weijiang
2023-11-03 22:26 ` Sean Christopherson
2023-09-14 6:33 ` [PATCH v6 20/25] KVM: x86: Save and reload SSP to/from SMRAM Yang Weijiang
2023-10-31 17:55 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 21/25] KVM: VMX: Set up interception for CET MSRs Yang Weijiang
2023-10-31 17:56 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 22/25] KVM: VMX: Set host constant supervisor states to VMCS fields Yang Weijiang
2023-10-31 17:56 ` Maxim Levitsky
2023-09-14 6:33 ` [PATCH v6 23/25] KVM: x86: Enable CET virtualization for VMX and advertise to userspace Yang Weijiang
2023-09-24 13:38 ` kernel test robot
2023-09-25 0:26 ` Yang, Weijiang
2023-10-31 17:56 ` Maxim Levitsky
2023-11-01 22:14 ` Sean Christopherson [this message]
2023-09-14 6:33 ` [PATCH v6 24/25] KVM: nVMX: Introduce new VMX_BASIC bit for event error_code delivery to L1 Yang Weijiang
2023-10-31 17:57 ` Maxim Levitsky
2023-11-01 4:21 ` Chao Gao
2023-11-15 8:31 ` Yang, Weijiang
2023-11-15 13:27 ` Sean Christopherson
2023-09-14 6:33 ` [PATCH v6 25/25] KVM: nVMX: Enable CET support for nested guest Yang Weijiang
2023-10-31 17:57 ` Maxim Levitsky
2023-11-01 2:09 ` Chao Gao
2023-11-01 9:22 ` Yang, Weijiang
2023-11-01 9:54 ` Maxim Levitsky
2023-11-15 8:56 ` Yang, Weijiang
2023-11-15 8:23 ` Yang, Weijiang
2023-09-25 0:31 ` [PATCH v6 00/25] Enable CET Virtualization Yang, Weijiang
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