linux-kernel - RE: [PATCH 6/7] KVM: VMX: Provide separate subroutines for invoking NMI vs. IRQ handlers

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Date:   Wed, 14 Dec 2022 21:23:05 +0000
From:   "Li, Xin3" <xin3.li@...el.com>
To:     "Christopherson,, Sean" <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Lutomirski, Andy" <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: RE: [PATCH 6/7] KVM: VMX: Provide separate subroutines for invoking
 NMI vs. IRQ handlers

> +
> +	/*
> +	 * "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?

> +.endm
> +
>  .section .noinstr.text, "ax"