Re: [PATCH v1 05/23] KVM: VMX: Initialize FRED VM entry/exit controls in vmcs_config

[Chao Gao]

On Wed, Nov 08, 2023 at 10:29:45AM -0800, Xin Li wrote:
>Setup the global vmcs_config for FRED:
>1) Add VM_ENTRY_LOAD_IA32_FRED to KVM_OPTIONAL_VMX_VM_ENTRY_CONTROLS to
>   have a FRED CPU load guest FRED MSRs from VMCS upon VM entry.
>2) Add SECONDARY_VM_EXIT_SAVE_IA32_FRED to
>   KVM_OPTIONAL_VMX_SECONDARY_VM_EXIT_CONTROLS to have a FRED CPU save
>   guest FRED MSRs to VMCS during VM exit.
>3) add SECONDARY_VM_EXIT_LOAD_IA32_FRED to
>   KVM_OPTIONAL_VMX_SECONDARY_VM_EXIT_CONTROLS to have a FRED CPU load
>   host FRED MSRs from VMCS during VM exit.
>
>Also add sanity checks to make sure FRED VM entry/exit controls can be
>set on a FRED CPU.
>
>Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
>Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
>---
> arch/x86/include/asm/vmx.h |  3 +++
> arch/x86/kvm/vmx/vmx.c     | 19 ++++++++++++++++++-
> arch/x86/kvm/vmx/vmx.h     |  7 +++++--
> 3 files changed, 26 insertions(+), 3 deletions(-)
>
>diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
>index 4d4177ec802c..41796a733bc9 100644
>--- a/arch/x86/include/asm/vmx.h
>+++ b/arch/x86/include/asm/vmx.h
>@@ -106,6 +106,8 @@
> #define VM_EXIT_PT_CONCEAL_PIP			0x01000000
> #define VM_EXIT_CLEAR_IA32_RTIT_CTL		0x02000000
> #define VM_EXIT_ACTIVATE_SECONDARY_CONTROLS	0x80000000
>+#define SECONDARY_VM_EXIT_SAVE_IA32_FRED	0x00000001
>+#define SECONDARY_VM_EXIT_LOAD_IA32_FRED	0x00000002
> 
> #define VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR	0x00036dff
> 
>@@ -119,6 +121,7 @@
> #define VM_ENTRY_LOAD_BNDCFGS                   0x00010000
> #define VM_ENTRY_PT_CONCEAL_PIP			0x00020000
> #define VM_ENTRY_LOAD_IA32_RTIT_CTL		0x00040000
>+#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 df769207cbe0..9186f41974ab 100644
>--- a/arch/x86/kvm/vmx/vmx.c
>+++ b/arch/x86/kvm/vmx/vmx.c
>@@ -2694,10 +2694,27 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> 		_vmexit_control &= ~x_ctrl;
> 	}
> 
>-	if (_vmexit_control & VM_EXIT_ACTIVATE_SECONDARY_CONTROLS)
>+	if (_vmexit_control & VM_EXIT_ACTIVATE_SECONDARY_CONTROLS) {
> 		_secondary_vmexit_control =
> 			adjust_vmx_controls64(KVM_OPTIONAL_VMX_SECONDARY_VM_EXIT_CONTROLS,
> 					      MSR_IA32_VMX_EXIT_CTLS2);
>+		if (cpu_feature_enabled(X86_FEATURE_FRED) &&
>+		    !(_secondary_vmexit_control & SECONDARY_VM_EXIT_SAVE_IA32_FRED &&
>+		      _secondary_vmexit_control & SECONDARY_VM_EXIT_LOAD_IA32_FRED)) {
>+			pr_warn_once("FRED enabled but no VMX VM-Exit {SAVE,LOAD}_IA32_FRED controls: %llx\n",
>+				     _secondary_vmexit_control);

if there is no VM_EXIT_ACTIVATE_SECONDARY_CONTROLS, shouldn't we also emit this
warning?

>+			if (error_on_inconsistent_vmcs_config)
>+				return -EIO;
>+		}
>+	}
>+
>+	if (cpu_feature_enabled(X86_FEATURE_FRED) &&
>+	    !(_vmentry_control & VM_ENTRY_LOAD_IA32_FRED)) {
>+		pr_warn_once("FRED enabled but no VMX VM-Entry LOAD_IA32_FRED control: %x\n",
>+			     _vmentry_control);

Can we just hide FRED from guests like what KVM does for other features which
have similar dependencies? see vmx_set_cpu_caps().