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Subject: Re: [PATCH 22/24] x86/entry: Implement and use do_paranoid_entry()
 and paranoid_exit()
To:     Peter Zijlstra <peterz@infradead.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>
Cc:     linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Joerg Roedel <jroedel@suse.de>,
        Youquan Song <youquan.song@intel.com>,
        Tony Luck <tony.luck@intel.com>
References: <20210831175025.27570-1-jiangshanlai@gmail.com>
 <20210831175025.27570-23-jiangshanlai@gmail.com>
 <YTCoenvIaHjLQmAC@hirez.programming.kicks-ass.net>
From:   Lai Jiangshan <laijs@linux.alibaba.com>
Message-ID: <44e08066-bbfb-222e-dffc-63e5b64f125f@linux.alibaba.com>
Date:   Thu, 2 Sep 2021 19:58:51 +0800
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On 2021/9/2 18:33, Peter Zijlstra wrote:
> On Wed, Sep 01, 2021 at 01:50:23AM +0800, Lai Jiangshan wrote:
> 
>> +	call	do_paranoid_entry
>>   	ret
> 
> That's normally spelled like:
> 
> 	jmp do_paranoid_entry
> 
> But the same comment as for error_entry but more; pretty much all that's
> left in asm is things like:
> 
> 
> 	call paranoid_entry;
> 
> 	# setup args
> 	call \cfunc
> 
> 	call paranoid_exit
> 
> which seems like prime material to also pull into C to avoid the
> back-and-forth thing. In fact, why can't you call paranoid_entry/exit
> from \cfunc itself? The IDT macros should be able to help.
> 

Oh, #VC will need to switch stack.  I think we need ASM code to switch
stack since the original stack need to be "free" for next #VC.