KVM: nVMX: Allow the caller to provide instruction length on nested VM-Exit

Rework the nested VM-Exit helper to take the instruction length as a
parameter, and convert nested_vmx_vmexit() into a "default" wrapper that
grabs the length from vmcs02 as appropriate.  This will allow KVM to set
the correct instruction length when synthesizing a nested VM-Exit when
emulating an instruction that L1 wants to intercept.

No functional change intended, as the path to prepare_vmcs12()'s reading
of vmcs02.VM_EXIT_INSTRUCTION_LEN is gated on the same set of conditions
as the VMREAD in the new nested_vmx_vmexit().

Link: https://lore.kernel.org/r/20250201015518.689704-10-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 e5c17fba65070418705e98291fc419bd61b1219a..edc2d2039508df9bcf739d89a90b85658f8d763e 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4618,7 +4618,7 @@ static void sync_vmcs02_to_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
  */
 static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
                           u32 vm_exit_reason, u32 exit_intr_info,
-                          unsigned long exit_qualification)
+                          unsigned long exit_qualification, u32 exit_insn_len)
 {
        /* update exit information fields: */
        vmcs12->vm_exit_reason = vm_exit_reason;
@@ -4646,7 +4646,7 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
                                          vm_exit_reason, exit_intr_info);
 
                vmcs12->vm_exit_intr_info = exit_intr_info;
-               vmcs12->vm_exit_instruction_len = vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
+               vmcs12->vm_exit_instruction_len = exit_insn_len;
                vmcs12->vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
 
                /*
@@ -4930,8 +4930,9 @@ vmabort:
  * and modify vmcs12 to make it see what it would expect to see there if
  * L2 was its real guest. Must only be called when in L2 (is_guest_mode())
  */
-void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
-                      u32 exit_intr_info, unsigned long exit_qualification)
+void __nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
+                        u32 exit_intr_info, unsigned long exit_qualification,
+                        u32 exit_insn_len)
 {
        struct vcpu_vmx *vmx = to_vmx(vcpu);
        struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
@@ -4981,7 +4982,8 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
 
                if (vm_exit_reason != -1)
                        prepare_vmcs12(vcpu, vmcs12, vm_exit_reason,
-                                      exit_intr_info, exit_qualification);
+                                      exit_intr_info, exit_qualification,
+                                      exit_insn_len);
 
                /*
                 * Must happen outside of sync_vmcs02_to_vmcs12() as it will

diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h
index 2c296b6abb8ccf0ed56459d479fd8eac281b06fe..6eedcfc91070c4518ebcb4a846a5e14eb26740b4 100644 (file)
--- a/arch/x86/kvm/vmx/nested.h
+++ b/arch/x86/kvm/vmx/nested.h
@@ -26,8 +26,26 @@ void nested_vmx_free_vcpu(struct kvm_vcpu *vcpu);
 enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
                                                     bool from_vmentry);
 bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu);
-void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
-                      u32 exit_intr_info, unsigned long exit_qualification);
+void __nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
+                        u32 exit_intr_info, unsigned long exit_qualification,
+                        u32 exit_insn_len);
+
+static inline void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
+                                    u32 exit_intr_info,
+                                    unsigned long exit_qualification)
+{
+       u32 exit_insn_len;
+
+       if (to_vmx(vcpu)->fail || vm_exit_reason == -1 ||
+           (vm_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
+               exit_insn_len = 0;
+       else
+               exit_insn_len = vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
+
+       __nested_vmx_vmexit(vcpu, vm_exit_reason, exit_intr_info,
+                           exit_qualification, exit_insn_len);
+}
+
 void nested_sync_vmcs12_to_shadow(struct kvm_vcpu *vcpu);
 int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data);
 int vmx_get_vmx_msr(struct nested_vmx_msrs *msrs, u32 msr_index, u64 *pdata);