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Subject[PATCH v2 06/25] KVM: VMX: Defer enabling FRED MSRs save/load until after set CPUID
Date
Clear FRED VM entry/exit controls when initializing a vCPU, and set
these controls only if FRED is enumerated after set CPUID.

FRED VM entry/exit controls need to be set to establish context
sufficient to support FRED event delivery immediately after VM entry
and exit. However it is not required to save/load FRED MSRs for
a non-FRED guest, which aren't supposed to access FRED MSRs.

Signed-off-by: Xin Li <xin3.li@intel.com>
Tested-by: Shan Kang <shan.kang@intel.com>
---

Changes since v1:
* Use kvm_cpu_cap_has() instead of cpu_feature_enabled() (Chao Gao).
* Clear FRED VM entry/exit controls if FRED is not enumerated (Chao Gao).
* Use guest_can_use() to trace FRED enumeration in a vcpu (Chao Gao).
---
arch/x86/kvm/governed_features.h | 1 +
arch/x86/kvm/vmx/vmx.c | 32 +++++++++++++++++++++++++++++++-
2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/governed_features.h b/arch/x86/kvm/governed_features.h
index ad463b1ed4e4..507ca73e52e9 100644
--- a/arch/x86/kvm/governed_features.h
+++ b/arch/x86/kvm/governed_features.h
@@ -17,6 +17,7 @@ KVM_GOVERNED_X86_FEATURE(PFTHRESHOLD)
KVM_GOVERNED_X86_FEATURE(VGIF)
KVM_GOVERNED_X86_FEATURE(VNMI)
KVM_GOVERNED_X86_FEATURE(LAM)
+KVM_GOVERNED_X86_FEATURE(FRED)

#undef KVM_GOVERNED_X86_FEATURE
#undef KVM_GOVERNED_FEATURE
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4023474ea002..34b6676f60d8 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4402,6 +4402,9 @@ static u32 vmx_vmentry_ctrl(void)
if (cpu_has_perf_global_ctrl_bug())
vmentry_ctrl &= ~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;

+ /* Whether to load guest FRED MSRs is deferred until after set CPUID */
+ vmentry_ctrl &= ~VM_ENTRY_LOAD_IA32_FRED;
+
return vmentry_ctrl;
}

@@ -4430,7 +4433,13 @@ static u32 vmx_vmexit_ctrl(void)

static u64 vmx_secondary_vmexit_ctrl(void)
{
- return vmcs_config.secondary_vmexit_ctrl;
+ u64 secondary_vmexit_ctrl = vmcs_config.secondary_vmexit_ctrl;
+
+ /* Whether to save/load FRED MSRs is deferred until after set CPUID */
+ secondary_vmexit_ctrl &= ~(SECONDARY_VM_EXIT_SAVE_IA32_FRED |
+ SECONDARY_VM_EXIT_LOAD_IA32_FRED);
+
+ return secondary_vmexit_ctrl;
}

static void vmx_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
@@ -7762,10 +7771,31 @@ static void update_intel_pt_cfg(struct kvm_vcpu *vcpu)
vmx->pt_desc.ctl_bitmask &= ~(0xfULL << (32 + i * 4));
}

+static void vmx_vcpu_config_fred_after_set_cpuid(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+ kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_FRED);
+
+ if (guest_can_use(vcpu, X86_FEATURE_FRED)) {
+ vm_entry_controls_setbit(vmx, VM_ENTRY_LOAD_IA32_FRED);
+ secondary_vm_exit_controls_setbit(vmx,
+ SECONDARY_VM_EXIT_SAVE_IA32_FRED |
+ SECONDARY_VM_EXIT_LOAD_IA32_FRED);
+ } else {
+ vm_entry_controls_clearbit(vmx, VM_ENTRY_LOAD_IA32_FRED);
+ secondary_vm_exit_controls_clearbit(vmx,
+ SECONDARY_VM_EXIT_SAVE_IA32_FRED |
+ SECONDARY_VM_EXIT_LOAD_IA32_FRED);
+ }
+}
+
static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);

+ vmx_vcpu_config_fred_after_set_cpuid(vcpu);
+
/*
* XSAVES is effectively enabled if and only if XSAVE is also exposed
* to the guest. XSAVES depends on CR4.OSXSAVE, and CR4.OSXSAVE can be
--
2.43.0

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