[PATCH v8 02/21] KVM: VMX: Initialize VM entry/exit FRED controls in vmcs_config

Xin Li (Intel)
2025-10-14T01:11:12Z

Setup VM entry/exit FRED controls in the global vmcs_config for proper
FRED VMCS fields management:
1) load guest FRED state upon VM entry.
2) save guest FRED state during VM exit.
3) load host FRED state during VM exit.

Also add FRED control consistency checks to the existing VM entry/exit
consistency check framework.

Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Tested-by: Shan Kang <shan.kang@intel.com>
Tested-by: Xuelian Guo <xuelian.guo@intel.com>
Reviewed-by: Chao Gao <chao.gao@intel.com>
---

Change in v5:
* Remove the pair VM_ENTRY_LOAD_IA32_FRED/VM_EXIT_ACTIVATE_SECONDARY_CONTROLS,
since the secondary VM exit controls are unconditionally enabled anyway, and
there are features other than FRED needing it (Chao Gao).
* Add TB from Xuelian Guo.

Change in v4:
* Do VM exit/entry consistency checks using the new macro from Sean
Christopherson.

Changes in v3:
* Add FRED control consistency checks to the existing VM entry/exit
consistency check framework (Sean Christopherson).
* Just do the unnecessary FRED state load/store on every VM entry/exit
(Sean Christopherson).
---
arch/x86/include/asm/vmx.h | 4 ++++
arch/x86/kvm/vmx/vmx.c | 2 ++
arch/x86/kvm/vmx/vmx.h | 7 +++++--
3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 1f60c04d11fb..dd79d027ea70 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -109,6 +109,9 @@
#define VM_EXIT_LOAD_CET_STATE 0x10000000
#define VM_EXIT_ACTIVATE_SECONDARY_CONTROLS 0x80000000

+#define SECONDARY_VM_EXIT_SAVE_IA32_FRED BIT_ULL(0)
+#define SECONDARY_VM_EXIT_LOAD_IA32_FRED BIT_ULL(1)
+
#define VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR 0x00036dff

#define VM_ENTRY_LOAD_DEBUG_CONTROLS 0x00000004
@@ -122,6 +125,7 @@
#define VM_ENTRY_PT_CONCEAL_PIP 0x00020000
#define VM_ENTRY_LOAD_IA32_RTIT_CTL 0x00040000
#define VM_ENTRY_LOAD_CET_STATE 0x00100000
+#define VM_ENTRY_LOAD_IA32_FRED 0x00800000

#define VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR 0x000011ff

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 255158595e77..d881f1c133fa 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2622,6 +2622,8 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
u32 entry_control;
u64 exit_control;
} const vmcs_entry_exit2_pairs[] = {
+ { VM_ENTRY_LOAD_IA32_FRED,
+ SECONDARY_VM_EXIT_SAVE_IA32_FRED | SECONDARY_VM_EXIT_LOAD_IA32_FRED },
};

memset(vmcs_conf, 0, sizeof(*vmcs_conf));
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index b2724aab48d2..2cf599211ab3 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -488,7 +488,8 @@ static inline u8 vmx_get_rvi(void)
VM_ENTRY_LOAD_BNDCFGS | \
VM_ENTRY_PT_CONCEAL_PIP | \
VM_ENTRY_LOAD_IA32_RTIT_CTL | \
- VM_ENTRY_LOAD_CET_STATE)
+ VM_ENTRY_LOAD_CET_STATE | \
+ VM_ENTRY_LOAD_IA32_FRED)

#define __KVM_REQUIRED_VMX_VM_EXIT_CONTROLS \
(VM_EXIT_SAVE_DEBUG_CONTROLS | \
@@ -515,7 +516,9 @@ static inline u8 vmx_get_rvi(void)
VM_EXIT_ACTIVATE_SECONDARY_CONTROLS)

#define KVM_REQUIRED_VMX_SECONDARY_VM_EXIT_CONTROLS (0)
-#define KVM_OPTIONAL_VMX_SECONDARY_VM_EXIT_CONTROLS (0)
+#define KVM_OPTIONAL_VMX_SECONDARY_VM_EXIT_CONTROLS \
+ (SECONDARY_VM_EXIT_SAVE_IA32_FRED | \
+ SECONDARY_VM_EXIT_LOAD_IA32_FRED)

#define KVM_REQUIRED_VMX_PIN_BASED_VM_EXEC_CONTROL \
(PIN_BASED_EXT_INTR_MASK | \
--
2.51.0