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bh=Uv5NXvZAXmi5JcnTTPv3AnGIZ1+vXF1EKPUlOm+C42U=; b=C0FTN5mmmN697p/fBd8yakE4dkg3cM5USnk/1nIeZ8vS6jfc6fhScfe+ RVICkh9mEBBTIJx5T7iQpRxNw0+ZP7v0qaBrpCPhoZLaFV5kLUi0g+ZRV pWA5ghEiP3WnkmzvjPRAb1r8W04ZtZUqwXzhGWZW0tYGBfPFlFLZ6P21S n7VADNg7yI/OtLjoZYHRxJjJSqvIc5Pzf9qf4LC5GV1CmLEYprbySd0v4 wstOWmUDUXk26VZXkgeR51PGaXMMmdQyiSkcLK0/HgUSQmD/O2y/V2hVB Z2GRvHoeuPrKCUkQmWLtzJGVYtVbfSVwWP75bAW+3WRv5m7g6scON1sVu g==; X-IronPort-AV: E=McAfee;i="6600,9927,10988"; a="2535163" X-IronPort-AV: E=Sophos;i="6.06,170,1705392000"; d="scan'208";a="2535163" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orvoesa108.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Feb 2024 23:47:45 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10988"; a="826966127" X-IronPort-AV: E=Sophos;i="6.06,170,1705392000"; d="scan'208";a="826966127" Received: from jf.jf.intel.com (HELO jf.intel.com) ([10.165.9.183]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Feb 2024 23:47:44 -0800 From: Yang Weijiang To: seanjc@google.com, pbonzini@redhat.com, dave.hansen@intel.com, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: peterz@infradead.org, chao.gao@intel.com, rick.p.edgecombe@intel.com, mlevitsk@redhat.com, john.allen@amd.com, weijiang.yang@intel.com Subject: [PATCH v10 23/27] KVM: VMX: Set host constant supervisor states to VMCS fields Date: Sun, 18 Feb 2024 23:47:29 -0800 Message-ID: <20240219074733.122080-24-weijiang.yang@intel.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240219074733.122080-1-weijiang.yang@intel.com> References: <20240219074733.122080-1-weijiang.yang@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1791313406846668926 X-GMAIL-MSGID: 1791313406846668926 Save constant values to HOST_{S_CET,SSP,INTR_SSP_TABLE} field explicitly. Kernel IBT is supported and the setting in MSR_IA32_S_CET is static after post-boot(The exception is BIOS call case but vCPU thread never across it) and KVM doesn't need to refresh HOST_S_CET field before every VM-Enter/ VM-Exit sequence. Host supervisor shadow stack is not enabled now and SSP is not accessible to kernel mode, thus it's safe to set host IA32_INT_SSP_TAB/SSP VMCS field to 0s. When shadow stack is enabled for CPL3, SSP is reloaded from PL3_SSP before it exits to userspace. Check SDM Vol 2A/B Chapter 3/4 for SYSCALL/ SYSRET/SYSENTER SYSEXIT/RDSSP/CALL etc. Prevent KVM module loading if host supervisor shadow stack SHSTK_EN is set in MSR_IA32_S_CET as KVM cannot co-exit with it correctly. Suggested-by: Sean Christopherson Suggested-by: Chao Gao Signed-off-by: Yang Weijiang Reviewed-by: Maxim Levitsky Reviewed-by: Chao Gao --- arch/x86/kvm/vmx/capabilities.h | 4 ++++ arch/x86/kvm/vmx/vmx.c | 15 +++++++++++++++ arch/x86/kvm/x86.c | 14 ++++++++++++++ arch/x86/kvm/x86.h | 1 + 4 files changed, 34 insertions(+) diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h index 41a4533f9989..ee8938818c8a 100644 --- a/arch/x86/kvm/vmx/capabilities.h +++ b/arch/x86/kvm/vmx/capabilities.h @@ -106,6 +106,10 @@ static inline bool cpu_has_load_perf_global_ctrl(void) return vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL; } +static inline bool cpu_has_load_cet_ctrl(void) +{ + return (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_CET_STATE); +} static inline bool cpu_has_vmx_mpx(void) { return vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_BNDCFGS; diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 24e921c4e7e3..342b5b94c892 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -4371,6 +4371,21 @@ void vmx_set_constant_host_state(struct vcpu_vmx *vmx) if (cpu_has_load_ia32_efer()) vmcs_write64(HOST_IA32_EFER, host_efer); + + /* + * Supervisor shadow stack is not enabled on host side, i.e., + * host IA32_S_CET.SHSTK_EN bit is guaranteed to 0 now, per SDM + * description(RDSSP instruction), SSP is not readable in CPL0, + * so resetting the two registers to 0s at VM-Exit does no harm + * to kernel execution. When execution flow exits to userspace, + * SSP is reloaded from IA32_PL3_SSP. Check SDM Vol.2A/B Chapter + * 3 and 4 for details. + */ + if (cpu_has_load_cet_ctrl()) { + vmcs_writel(HOST_S_CET, host_s_cet); + vmcs_writel(HOST_SSP, 0); + vmcs_writel(HOST_INTR_SSP_TABLE, 0); + } } void set_cr4_guest_host_mask(struct vcpu_vmx *vmx) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 281c3fe728c5..73a55d388dd9 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -114,6 +114,8 @@ static u64 __read_mostly efer_reserved_bits = ~((u64)EFER_SCE); #endif static u64 __read_mostly cr4_reserved_bits = CR4_RESERVED_BITS; +u64 __read_mostly host_s_cet; +EXPORT_SYMBOL_GPL(host_s_cet); #define KVM_EXIT_HYPERCALL_VALID_MASK (1 << KVM_HC_MAP_GPA_RANGE) @@ -9862,6 +9864,18 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops) return -EIO; } + if (boot_cpu_has(X86_FEATURE_SHSTK)) { + rdmsrl(MSR_IA32_S_CET, host_s_cet); + /* + * Linux doesn't yet support supervisor shadow stacks (SSS), so + * KVM doesn't save/restore the associated MSRs, i.e. KVM may + * clobber the host values. Yell and refuse to load if SSS is + * unexpectedly enabled, e.g. to avoid crashing the host. + */ + if (WARN_ON_ONCE(host_s_cet & CET_SHSTK_EN)) + return -EIO; + } + x86_emulator_cache = kvm_alloc_emulator_cache(); if (!x86_emulator_cache) { pr_err("failed to allocate cache for x86 emulator\n"); diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index 9c19dfb5011d..656107e64c93 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -325,6 +325,7 @@ fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu); extern u64 host_xcr0; extern u64 host_xss; extern u64 host_arch_capabilities; +extern u64 host_s_cet; extern struct kvm_caps kvm_caps;