linux-kernel - [PATCH v3 24/25] KVM: VMX: Cache MSR_IA32_VMX_MISC in vmcs

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Message-Id: <20220708144223.610080-25-vkuznets@redhat.com>
Date:   Fri,  8 Jul 2022 16:42:22 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 24/25] KVM: VMX: Cache MSR_IA32_VMX_MISC in vmcs_config

Like other host VMX control MSRs, MSR_IA32_VMX_MISC can be cached in
vmcs_config to avoid the need to re-read it later, e.g. from
cpu_has_vmx_intel_pt() or cpu_has_vmx_shadow_vmcs().

No (real) functional change intended.

Reviewed-by: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/vmx/capabilities.h | 11 +++--------
 arch/x86/kvm/vmx/vmx.c          |  8 +++++---
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index 07e7492fe72a..07f7a9534211 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -65,6 +65,7 @@ struct vmcs_config {
 	u64 cpu_based_3rd_exec_ctrl;
 	u32 vmexit_ctrl;
 	u32 vmentry_ctrl;
+	u64 misc;
 	struct nested_vmx_msrs nested;
 };
 extern struct vmcs_config vmcs_config;
@@ -225,11 +226,8 @@ static inline bool cpu_has_vmx_vmfunc(void)
 
 static inline bool cpu_has_vmx_shadow_vmcs(void)
 {
-	u64 vmx_msr;
-
 	/* check if the cpu supports writing r/o exit information fields */
-	rdmsrl(MSR_IA32_VMX_MISC, vmx_msr);
-	if (!(vmx_msr & MSR_IA32_VMX_MISC_VMWRITE_SHADOW_RO_FIELDS))
+	if (!(vmcs_config.misc & MSR_IA32_VMX_MISC_VMWRITE_SHADOW_RO_FIELDS))
 		return false;
 
 	return vmcs_config.cpu_based_2nd_exec_ctrl &
@@ -371,10 +369,7 @@ static inline bool cpu_has_vmx_invvpid_global(void)
 
 static inline bool cpu_has_vmx_intel_pt(void)
 {
-	u64 vmx_msr;
-
-	rdmsrl(MSR_IA32_VMX_MISC, vmx_msr);
-	return (vmx_msr & MSR_IA32_VMX_MISC_INTEL_PT) &&
+	return (vmcs_config.misc & MSR_IA32_VMX_MISC_INTEL_PT) &&
 		(vmcs_config.cpu_based_2nd_exec_ctrl & SECONDARY_EXEC_PT_USE_GPA) &&
 		(vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_RTIT_CTL);
 }
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 35285109856f..ab091758c437 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2479,6 +2479,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 	u64 _cpu_based_3rd_exec_control = 0;
 	u32 _vmexit_control = 0;
 	u32 _vmentry_control = 0;
+	u64 misc_msr;
 	int i;
 
 	/*
@@ -2613,6 +2614,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 	if (((vmx_msr_high >> 18) & 15) != 6)
 		return -EIO;
 
+	rdmsrl(MSR_IA32_VMX_MISC, misc_msr);
+
 	vmcs_conf->size = vmx_msr_high & 0x1fff;
 	vmcs_conf->basic_cap = vmx_msr_high & ~0x1fff;
 
@@ -2624,6 +2627,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 	vmcs_conf->cpu_based_3rd_exec_ctrl = _cpu_based_3rd_exec_control;
 	vmcs_conf->vmexit_ctrl         = _vmexit_control;
 	vmcs_conf->vmentry_ctrl        = _vmentry_control;
+	vmcs_conf->misc	= misc_msr;
 
 	return 0;
 }
@@ -8241,11 +8245,9 @@ static __init int hardware_setup(void)
 
 	if (enable_preemption_timer) {
 		u64 use_timer_freq = 5000ULL * 1000 * 1000;
-		u64 vmx_msr;
 
-		rdmsrl(MSR_IA32_VMX_MISC, vmx_msr);
 		cpu_preemption_timer_multi =
-			vmx_msr & VMX_MISC_PREEMPTION_TIMER_RATE_MASK;
+			vmcs_config.misc & VMX_MISC_PREEMPTION_TIMER_RATE_MASK;
 
 		if (tsc_khz)
 			use_timer_freq = (u64)tsc_khz * 1000;
-- 
2.35.3