On Wed, Dec 14, 2022, Li, Xin3 wrote: > > + > > + /* > > + * "Restore" RSP from RBP, even though IRET has already unwound > > RSP to > > + * the correct value. objtool doesn't know the callee will IRET and, > > + * without the explicit restore, thinks the stack is getting walloped. > > + * Using an unwind hint is problematic due to x86-64's dynamic > > alignment. > > + */ > > + mov %_ASM_BP, %_ASM_SP > > + pop %_ASM_BP > > + RET > > For NMI, after this RET instruction, we continue to block NMIs. IRET instead? No, IRET has already been done by the kernel-provided handler, e.g. asm_exc_nmi_kvm_vmx() by way of error_return(). That's why the CALL above (that got snipped) is preceded by the creation of a synthetic NMI/IRQ stack frame: the target returns from the CALL via IRET, not RET.
