On Wed, Nov 08, 2023 at 10:29:46AM -0800, Xin Li wrote:
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.
A non-FRED guest should get #GP upon accessing FRED MSRs, otherwise it corrupts host FRED MSRs.
Tested-by: Shan Kang shan.kang@intel.com Signed-off-by: Xin Li xin3.li@intel.com
arch/x86/kvm/vmx/vmx.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 9186f41974ab..5d4786812664 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -4423,6 +4423,9 @@ 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;
}
@@ -4458,7 +4461,13 @@ 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) @@ -7785,10 +7794,33 @@ 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);
- if (!cpu_feature_enabled(X86_FEATURE_FRED) ||
!guest_cpuid_has(vcpu, X86_FEATURE_FRED))return;- /* Enable loading guest FRED MSRs from VMCS */
- vm_entry_controls_setbit(vmx, VM_ENTRY_LOAD_IA32_FRED);
- /*
* Enable saving guest FRED MSRs into VMCS and loading host FRED MSRs* from VMCS.*/- vm_exit_controls_setbit(vmx, VM_EXIT_ACTIVATE_SECONDARY_CONTROLS);
- secondary_vm_exit_controls_setbit(vmx,
SECONDARY_VM_EXIT_SAVE_IA32_FRED |SECONDARY_VM_EXIT_LOAD_IA32_FRED);
all above vmcs controls need to be cleared if guest doesn't enumerate FRED, see
https://lore.kernel.org/all/ZJYzPn7ipYfO0fLZ@google.com/
Clearing VM_EXIT_ACTIVATE_SECONDARY_CONTROLS may be problematic when new bits are added to secondary vmcs controls. Why not keep VM_EXIT_ACTIVATE_SECONDARY_CONTROLS always on if it is supported? or you see any perf impact?
+}
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
-- 2.42.0