KVM: nVMX: Virtualize NO_HW_ERROR_CODE_CC for L1 event injection to L2

Per SDM description(Vol.3D, Appendix A.1):
"If bit 56 is read as 1, software can use VM entry to deliver a hardware
exception with or without an error code, regardless of vector"

Modify has_error_code check before inject events to nested guest. Only
enforce the check when guest is in real mode, the exception is not hard
exception and the platform doesn't enumerate bit56 in VMX_BASIC, in all
other case ignore the check to make the logic consistent with SDM.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Chao Gao <chao.gao@intel.com>
Tested-by: Mathias Krause <minipli@grsecurity.net>
Tested-by: John Allen <john.allen@amd.com>
Tested-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/r/20250919223258.1604852-31-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 846c07380eac05b498ad6533488faaa02ca0626a..b644f4599f70b953d16fbc3c34f4083a32fd3c97 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1272,9 +1272,10 @@ static int vmx_restore_vmx_basic(struct vcpu_vmx *vmx, u64 data)
 {
        const u64 feature_bits = VMX_BASIC_DUAL_MONITOR_TREATMENT |
                                 VMX_BASIC_INOUT |
-                                VMX_BASIC_TRUE_CTLS;
+                                VMX_BASIC_TRUE_CTLS |
+                                VMX_BASIC_NO_HW_ERROR_CODE_CC;
 
-       const u64 reserved_bits = GENMASK_ULL(63, 56) |
+       const u64 reserved_bits = GENMASK_ULL(63, 57) |
                                  GENMASK_ULL(47, 45) |
                                  BIT_ULL(31);
 
@@ -2949,7 +2950,6 @@ static int nested_check_vm_entry_controls(struct kvm_vcpu *vcpu,
                u8 vector = intr_info & INTR_INFO_VECTOR_MASK;
                u32 intr_type = intr_info & INTR_INFO_INTR_TYPE_MASK;
                bool has_error_code = intr_info & INTR_INFO_DELIVER_CODE_MASK;
-               bool should_have_error_code;
                bool urg = nested_cpu_has2(vmcs12,
                                           SECONDARY_EXEC_UNRESTRICTED_GUEST);
                bool prot_mode = !urg || vmcs12->guest_cr0 & X86_CR0_PE;
@@ -2966,12 +2966,19 @@ static int nested_check_vm_entry_controls(struct kvm_vcpu *vcpu,
                    CC(intr_type == INTR_TYPE_OTHER_EVENT && vector != 0))
                        return -EINVAL;
 
-               /* VM-entry interruption-info field: deliver error code */
-               should_have_error_code =
-                       intr_type == INTR_TYPE_HARD_EXCEPTION && prot_mode &&
-                       x86_exception_has_error_code(vector);
-               if (CC(has_error_code != should_have_error_code))
-                       return -EINVAL;
+               /*
+                * Cannot deliver error code in real mode or if the interrupt
+                * type is not hardware exception. For other cases, do the
+                * consistency check only if the vCPU doesn't enumerate
+                * VMX_BASIC_NO_HW_ERROR_CODE_CC.
+                */
+               if (!prot_mode || intr_type != INTR_TYPE_HARD_EXCEPTION) {
+                       if (CC(has_error_code))
+                               return -EINVAL;
+               } else if (!nested_cpu_has_no_hw_errcode_cc(vcpu)) {
+                       if (CC(has_error_code != x86_exception_has_error_code(vector)))
+                               return -EINVAL;
+               }
 
                /* VM-entry exception error code */
                if (CC(has_error_code &&
@@ -7217,6 +7224,8 @@ static void nested_vmx_setup_basic(struct nested_vmx_msrs *msrs)
        msrs->basic |= VMX_BASIC_TRUE_CTLS;
        if (cpu_has_vmx_basic_inout())
                msrs->basic |= VMX_BASIC_INOUT;
+       if (cpu_has_vmx_basic_no_hw_errcode_cc())
+               msrs->basic |= VMX_BASIC_NO_HW_ERROR_CODE_CC;
 }
 
 static void nested_vmx_setup_cr_fixed(struct nested_vmx_msrs *msrs)

diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h
index 6eedcfc91070c4518ebcb4a846a5e14eb26740b4..983484d42ebf9d4a6f28d4916fa8262fffd8fb26 100644 (file)
--- a/arch/x86/kvm/vmx/nested.h
+++ b/arch/x86/kvm/vmx/nested.h
@@ -309,6 +309,11 @@ static inline bool nested_cr4_valid(struct kvm_vcpu *vcpu, unsigned long val)
               __kvm_is_valid_cr4(vcpu, val);
 }
 
+static inline bool nested_cpu_has_no_hw_errcode_cc(struct kvm_vcpu *vcpu)
+{
+       return to_vmx(vcpu)->nested.msrs.basic & VMX_BASIC_NO_HW_ERROR_CODE_CC;
+}
+
 /* No difference in the restrictions on guest and host CR4 in VMX operation. */
 #define nested_guest_cr4_valid nested_cr4_valid
 #define nested_host_cr4_valid  nested_cr4_valid