[RFC PATCH v6 21/36] KVM: nVMX: Always emulate PERF_GLOBAL_CTRL VM-Entry/VM-Exit controls

Sean Christopherson
2022-08-24T03:04:31Z

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@google.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 eed7551dd63c..6e9b32744e0d 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6611,11 +6611,12 @@ 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;
@@ -6630,10 +6631,10 @@ 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;
--
2.37.1.595.g718a3a8f04-goog