From: Sean Christopherson <seanjc@google.com>
To: Yang Weijiang <weijiang.yang@intel.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 21/27] KVM: x86: Save and reload SSP to/from SMRAM
Date: Wed, 1 May 2024 15:50:11 -0700 [thread overview]
Message-ID: <ZjLHIwCsLoatrxQ4@google.com> (raw)
In-Reply-To: <20240219074733.122080-22-weijiang.yang@intel.com>
On Sun, Feb 18, 2024, Yang Weijiang wrote:
> Save CET SSP to SMRAM on SMI and reload it on RSM. KVM emulates HW arch
> behavior when guest enters/leaves SMM mode,i.e., save registers to SMRAM
> at the entry of SMM and reload them at the exit to SMM. Per SDM, SSP is
> one of such registers on 64-bit Arch, and add the support for SSP. Note,
> on 32-bit Arch, SSP is not defined in SMRAM, so fail 32-bit CET guest
> launch.
>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
> arch/x86/kvm/cpuid.c | 11 +++++++++++
> arch/x86/kvm/smm.c | 8 ++++++++
> arch/x86/kvm/smm.h | 2 +-
> 3 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 2bb1931103ad..c0e13040e35b 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -149,6 +149,17 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu,
> if (vaddr_bits != 48 && vaddr_bits != 57 && vaddr_bits != 0)
> return -EINVAL;
> }
> + /*
> + * Prevent 32-bit guest launch if shadow stack is exposed as SSP
> + * state is not defined for 32-bit SMRAM.
Why? Lack of save/restore for SSP on 32-bit guests is a gap in Intel's
architecture, I don't see why KVM should diverge from hardware. I.e. just do
nothing for SSP on SMI/RSM, because that's exactly what the architecture says
will happen.
> + */
> + best = cpuid_entry2_find(entries, nent, 0x80000001,
> + KVM_CPUID_INDEX_NOT_SIGNIFICANT);
> + if (best && !(best->edx & F(LM))) {
> + best = cpuid_entry2_find(entries, nent, 0x7, 0);
> + if (best && (best->ecx & F(SHSTK)))
> + return -EINVAL;
> + }
>
> /*
> * Exposing dynamic xfeatures to the guest requires additional
> diff --git a/arch/x86/kvm/smm.c b/arch/x86/kvm/smm.c
> index 45c855389ea7..7aac9c54c353 100644
> --- a/arch/x86/kvm/smm.c
> +++ b/arch/x86/kvm/smm.c
> @@ -275,6 +275,10 @@ static void enter_smm_save_state_64(struct kvm_vcpu *vcpu,
> enter_smm_save_seg_64(vcpu, &smram->gs, VCPU_SREG_GS);
>
> smram->int_shadow = static_call(kvm_x86_get_interrupt_shadow)(vcpu);
> +
> + if (guest_can_use(vcpu, X86_FEATURE_SHSTK))
> + KVM_BUG_ON(kvm_msr_read(vcpu, MSR_KVM_SSP, &smram->ssp),
> + vcpu->kvm);
> }
> #endif
>
> @@ -564,6 +568,10 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
> static_call(kvm_x86_set_interrupt_shadow)(vcpu, 0);
> ctxt->interruptibility = (u8)smstate->int_shadow;
>
> + if (guest_can_use(vcpu, X86_FEATURE_SHSTK))
> + KVM_BUG_ON(kvm_msr_write(vcpu, MSR_KVM_SSP, smstate->ssp),
> + vcpu->kvm);
This should synthesize triple-fault, not WARN and kill the VM, as the value to
be restored is guest controlled (the guest can scribble SMRAM from within the
SMI handler).
At that point, I would just synthesize triple-fault for the read path too.
next prev parent reply other threads:[~2024-05-01 22:50 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-19 7:47 [PATCH v10 00/27] Enable CET Virtualization Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 01/27] x86/fpu/xstate: Always preserve non-user xfeatures/flags in __state_perm Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 02/27] x86/fpu/xstate: Refine CET user xstate bit enabling Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 03/27] x86/fpu/xstate: Add CET supervisor mode state support Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 04/27] x86/fpu/xstate: Introduce XFEATURE_MASK_KERNEL_DYNAMIC xfeature set Yang Weijiang
2024-05-01 18:45 ` Sean Christopherson
2024-05-02 17:46 ` Dave Hansen
2024-05-07 22:57 ` Sean Christopherson
2024-05-07 23:17 ` Dave Hansen
2024-05-08 1:19 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 05/27] x86/fpu/xstate: Introduce fpu_guest_cfg for guest FPU configuration Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 06/27] x86/fpu/xstate: Create guest fpstate with guest specific config Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 07/27] x86/fpu/xstate: Warn if kernel dynamic xfeatures detected in normal fpstate Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 08/27] KVM: x86: Rework cpuid_get_supported_xcr0() to operate on vCPU data Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 09/27] KVM: x86: Rename kvm_{g,s}et_msr()* to menifest emulation operations Yang Weijiang
2024-05-01 18:54 ` Sean Christopherson
2024-05-06 5:58 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 10/27] KVM: x86: Refine xsave-managed guest register/MSR reset handling Yang Weijiang
2024-02-20 3:04 ` Chao Gao
2024-02-20 13:23 ` Yang, Weijiang
2024-05-01 20:40 ` Sean Christopherson
2024-05-06 7:26 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 11/27] KVM: x86: Add kvm_msr_{read,write}() helpers Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 12/27] KVM: x86: Report XSS as to-be-saved if there are supported features Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 13/27] KVM: x86: Refresh CPUID on write to guest MSR_IA32_XSS Yang Weijiang
2024-02-20 8:51 ` Chao Gao
2024-05-01 20:43 ` Sean Christopherson
2024-05-06 7:30 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 14/27] KVM: x86: Initialize kvm_caps.supported_xss Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 15/27] KVM: x86: Load guest FPU state when access XSAVE-managed MSRs Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 16/27] KVM: x86: Add fault checks for guest CR4.CET setting Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 17/27] KVM: x86: Report KVM supported CET MSRs as to-be-saved Yang Weijiang
2024-05-01 22:40 ` Sean Christopherson
2024-05-06 8:31 ` Yang, Weijiang
2024-05-07 17:27 ` Sean Christopherson
2024-05-08 7:00 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 18/27] KVM: VMX: Introduce CET VMCS fields and control bits Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 19/27] KVM: x86: Use KVM-governed feature framework to track "SHSTK/IBT enabled" Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 20/27] KVM: VMX: Emulate read and write to CET MSRs Yang Weijiang
2024-03-12 22:55 ` Sean Christopherson
2024-03-13 9:43 ` Yang, Weijiang
2024-03-13 16:00 ` Sean Christopherson
2024-02-19 7:47 ` [PATCH v10 21/27] KVM: x86: Save and reload SSP to/from SMRAM Yang Weijiang
2024-05-01 22:50 ` Sean Christopherson [this message]
2024-05-06 8:41 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 22/27] KVM: VMX: Set up interception for CET MSRs Yang Weijiang
2024-05-01 23:07 ` Sean Christopherson
2024-05-06 8:48 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 23/27] KVM: VMX: Set host constant supervisor states to VMCS fields Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 24/27] KVM: x86: Enable CET virtualization for VMX and advertise to userspace Yang Weijiang
2024-05-01 23:15 ` Sean Christopherson
2024-05-01 23:24 ` Edgecombe, Rick P
2024-05-06 9:19 ` Yang, Weijiang
2024-05-06 16:54 ` Sean Christopherson
2024-05-07 2:37 ` Yang, Weijiang
2024-05-06 17:05 ` Edgecombe, Rick P
2024-05-06 23:33 ` Sean Christopherson
2024-05-06 23:53 ` Edgecombe, Rick P
2024-05-07 14:21 ` Sean Christopherson
2024-05-07 14:45 ` Edgecombe, Rick P
2024-05-07 15:08 ` Sean Christopherson
2024-05-07 15:33 ` Edgecombe, Rick P
2024-05-16 7:13 ` Yang, Weijiang
2024-05-16 14:39 ` Sean Christopherson
2024-05-16 15:36 ` Dave Hansen
2024-05-16 16:58 ` Sean Christopherson
2024-05-17 8:27 ` Yang, Weijiang
2024-05-17 8:57 ` Thomas Gleixner
2024-05-17 14:26 ` Sean Christopherson
2024-05-20 9:43 ` Yang, Weijiang
2024-05-20 17:09 ` Sean Christopherson
2024-05-20 17:15 ` Dave Hansen
2024-05-22 9:03 ` Yang, Weijiang
2024-05-22 15:06 ` Edgecombe, Rick P
2024-05-23 10:07 ` Yang, Weijiang
2024-05-22 8:41 ` Yang, Weijiang
2024-05-27 9:05 ` Yang, Weijiang
2024-05-01 23:34 ` Sean Christopherson
2024-05-06 9:41 ` Yang, Weijiang
2024-05-16 7:20 ` Yang, Weijiang
2024-05-16 14:43 ` Sean Christopherson
2024-05-17 8:04 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 25/27] KVM: nVMX: Introduce new VMX_BASIC bit for event error_code delivery to L1 Yang Weijiang
2024-05-01 23:19 ` Sean Christopherson
2024-05-06 9:19 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 26/27] KVM: nVMX: Enable CET support for nested guest Yang Weijiang
2024-05-01 23:23 ` Sean Christopherson
2024-05-06 9:25 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 27/27] KVM: x86: Don't emulate instructions guarded by CET Yang Weijiang
2024-05-01 23:24 ` Sean Christopherson
2024-05-06 9:26 ` Yang, Weijiang
2024-03-06 14:44 ` [PATCH v10 00/27] Enable CET Virtualization Yang, Weijiang
2024-05-01 23:27 ` Sean Christopherson
2024-05-06 9:31 ` Yang, Weijiang
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