linux-kernel - [PATCH v4 15/20] KVM:VMX: Save host MSR_IA32_S

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Message-Id: <20230721030352.72414-16-weijiang.yang@intel.com>
Date:   Thu, 20 Jul 2023 23:03:47 -0400
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     seanjc@...gle.com, pbonzini@...hat.com, peterz@...radead.org,
        john.allen@....com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     rick.p.edgecombe@...el.com, chao.gao@...el.com,
        binbin.wu@...ux.intel.com, weijiang.yang@...el.com
Subject: [PATCH v4 15/20] KVM:VMX: Save host MSR_IA32_S_CET to VMCS field

Save host MSR_IA32_S_CET to VMCS field as host constant state.
Kernel IBT is supported now and the setting in MSR_IA32_S_CET
is static after post-boot except in BIOS call case, but vCPU
won't execute such BIOS call path currently, so it's safe to
make the MSR as host constant.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kvm/vmx/capabilities.h | 4 ++++
 arch/x86/kvm/vmx/vmx.c          | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index d0abee35d7ba..b1883f6c08eb 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 85cb7e748a89..cba24acf1a7a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -109,6 +109,8 @@ module_param(enable_apicv, bool, S_IRUGO);
 bool __read_mostly enable_ipiv = true;
 module_param(enable_ipiv, bool, 0444);
 
+static u64 __read_mostly host_s_cet;
+
 /*
  * If nested=1, nested virtualization is supported, i.e., guests may use
  * VMX and be a hypervisor for its own guests. If nested=0, guests may not
@@ -4355,6 +4357,9 @@ void vmx_set_constant_host_state(struct vcpu_vmx *vmx)
 
 	if (cpu_has_load_ia32_efer())
 		vmcs_write64(HOST_IA32_EFER, host_efer);
+
+	if (cpu_has_load_cet_ctrl())
+		vmcs_writel(HOST_S_CET, host_s_cet);
 }
 
 void set_cr4_guest_host_mask(struct vcpu_vmx *vmx)
@@ -8633,6 +8638,9 @@ static __init int hardware_setup(void)
 			return r;
 	}
 
+	if (cpu_has_load_cet_ctrl())
+		rdmsrl_safe(MSR_IA32_S_CET, &host_s_cet);
+
 	vmx_set_cpu_caps();
 
 	r = alloc_kvm_area();
-- 
2.27.0