linux-kernel - Re: [patch V2 06/17] x86/entry/32: Remove redundant interrupt disable

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Date:   Wed, 23 Oct 2019 07:17:59 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Will Deacon <will@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-arch@...r.kernel.org, Mike Rapoport <rppt@...ux.ibm.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>
Subject: Re: [patch V2 06/17] x86/entry/32: Remove redundant interrupt disable

On Wed, Oct 23, 2019 at 02:27:11PM +0200, Thomas Gleixner wrote:
> Now that the trap handlers return with interrupts disabled, the
> unconditional disabling of interrupts in the low level entry code can be
> removed along with the trace calls and the misnomed preempt_stop macro.
> As a consequence ret_from_exception and ret_from_intr collapse.
> 
> Add a debug check to verify that interrupts are disabled depending on
> CONFIG_DEBUG_ENTRY.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---

One nit below.

Reviewed-by: Sean Christopherson <sean.j.christopherson@...el.com>

>  arch/x86/entry/entry_32.S |   21 ++++++---------------
>  1 file changed, 6 insertions(+), 15 deletions(-)
> 
> --- a/arch/x86/entry/entry_32.S
> +++ b/arch/x86/entry/entry_32.S
> @@ -1207,7 +1198,7 @@ ENDPROC(common_spurious)
>  	TRACE_IRQS_OFF
>  	movl	%esp, %eax
>  	call	do_IRQ
> -	jmp	ret_from_intr
> +	jmp	ret_from_exception
>  ENDPROC(common_interrupt)
>  
>  #define BUILD_INTERRUPT3(name, nr, fn)			\
> @@ -1219,7 +1210,7 @@ ENTRY(name)						\
>  	TRACE_IRQS_OFF					\
>  	movl	%esp, %eax;				\
>  	call	fn;					\
> -	jmp	ret_from_intr;				\
> +	jmp	ret_from_exception;				\

This backslash is now unaligned.

>  ENDPROC(name)
>  
>  #define BUILD_INTERRUPT(name, nr)		\
> @@ -1366,7 +1357,7 @@ ENTRY(xen_do_upcall)
>  #ifndef CONFIG_PREEMPTION
>  	call	xen_maybe_preempt_hcall
>  #endif
> -	jmp	ret_from_intr
> +	jmp	ret_from_exception
>  ENDPROC(xen_hypervisor_callback)
>  
>  /*
> 
>