linux-kernel - [PATCH v6 18/33] KVM: nVMX: Always emulate PERF_GLOBAL

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Date:   Tue, 30 Aug 2022 15:37:22 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Yuan Yao <yuan.yao@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v6 18/33] KVM: nVMX: Always emulate PERF_GLOBAL_CTRL VM-Entry/VM-Exit controls

From: Sean Christopherson <seanjc@...gle.com>

Advertise VM_{ENTRY,EXIT}_LOAD_IA32_PERF_GLOBAL_CTRL as being supported
for nested VMs irrespective of hardware support.  KVM fully emulates
the controls, i.e. manually emulates MSR writes on entry/exit, and never
propagates the guest settings directly to vmcs02.

In addition to allowing L1 VMMs to use the controls on older hardware,
unconditionally advertising the controls will also allow KVM to use its
vmcs01 configuration as the basis for the nested VMX configuration
without causing a regression (due the errata which causes KVM to "hide"
the control from vmcs01 but not vmcs12).

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/vmx/nested.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index c9b17239c9e8..19a96cf65b99 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6602,11 +6602,12 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps)
 		VM_EXIT_HOST_ADDR_SPACE_SIZE |
 #endif
 		VM_EXIT_LOAD_IA32_PAT | VM_EXIT_SAVE_IA32_PAT |
-		VM_EXIT_CLEAR_BNDCFGS | VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
+		VM_EXIT_CLEAR_BNDCFGS;
 	msrs->exit_ctls_high |=
 		VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR |
 		VM_EXIT_LOAD_IA32_EFER | VM_EXIT_SAVE_IA32_EFER |
-		VM_EXIT_SAVE_VMX_PREEMPTION_TIMER | VM_EXIT_ACK_INTR_ON_EXIT;
+		VM_EXIT_SAVE_VMX_PREEMPTION_TIMER | VM_EXIT_ACK_INTR_ON_EXIT |
+		VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
 
 	/* We support free control of debug control saving. */
 	msrs->exit_ctls_low &= ~VM_EXIT_SAVE_DEBUG_CONTROLS;
@@ -6621,10 +6622,10 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps)
 #ifdef CONFIG_X86_64
 		VM_ENTRY_IA32E_MODE |
 #endif
-		VM_ENTRY_LOAD_IA32_PAT | VM_ENTRY_LOAD_BNDCFGS |
-		VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
+		VM_ENTRY_LOAD_IA32_PAT | VM_ENTRY_LOAD_BNDCFGS;
 	msrs->entry_ctls_high |=
-		(VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR | VM_ENTRY_LOAD_IA32_EFER);
+		(VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR | VM_ENTRY_LOAD_IA32_EFER |
+		 VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL);
 
 	/* We support free control of debug control loading. */
 	msrs->entry_ctls_low &= ~VM_ENTRY_LOAD_DEBUG_CONTROLS;
-- 
2.37.2