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Subject: Re: [PATCH 01/23] x86, kaiser: prepare assembly for entry/exit CR3
 switching
To: Thomas Gleixner <tglx@linutronix.de>
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 <alpine.DEB.2.20.1711012155000.1942@nanos>
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From: Dave Hansen <dave.hansen@linux.intel.com>
Message-ID: <1417af11-44fc-e14c-9cfa-5938a18605e1@linux.intel.com>
Date: Wed, 1 Nov 2017 15:58:43 -0700
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On 11/01/2017 02:01 PM, Thomas Gleixner wrote:
> On Tue, 31 Oct 2017, Dave Hansen wrote:
>>  
>> +	pushq	%rdi
>> +	SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi
>> +	popq	%rdi
> 
> Can you please have a macro variant which does:
> 
>     SWITCH_TO_KERNEL_CR3_PUSH reg=%rdi
> 
> So the pushq/popq is inside the macro. This has two reasons:
> 
>    1) If KAISER=n the pointless pushq/popq go away
> 
>    2) We need a boottime switch for that stuff, so we better have all
>       related code in the various macros in order to patch it in/out.

After Boris's comments, these push/pops are totally unnecessary.  We
just delay the CR3 until after we stashed off pt_regs and are allowed to
clobber things.

> Also, please wrap these macros in #ifdef KAISER right away and provide the
> stubs as well. It does not make sense to have them in patch 7 when patch 1
> introduces them.

Will do.