linux-kernel - Re: [patch 3/3] x86/paravirt: Replace paravirt patch asm magic

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Message-ID: <6da95feb-e8ea-0c9b-d4c1-fa3556d6026a@suse.com>
Date:   Thu, 25 Apr 2019 09:46:15 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [patch 3/3] x86/paravirt: Replace paravirt patch asm magic

On 25/04/2019 09:22, Thomas Gleixner wrote:
> On Thu, 25 Apr 2019, Ingo Molnar wrote:
>>> +# else
>>> +	.irq_restore_fl		= { 0x50, 0x9d },	// push %eax; popf
>>> +	.mmu_write_cr3		= { 0x0f, 0x22, 0xd8 },	// mov %eax, %cr3
>>> +	.cpu_iret		= { 0xcf },		// iret
>>> +# endif
>>
>> I think these open-coded hexa versions are somewhat fragile as well, how 
>> about putting these into a .S file and controlling the sections in an LTO 
>> safe manner there?
>>
>> That will also allow us to write proper asm, and global labels can be 
>> used to extract the patchlets and their length?
> 
> We are not changing these any other day and I really don't see a reason to
> have these things global just because.

What about generating the hex values from the Makefile using a temporary
.S file? This would make the result easy verifiable and I don't think
setting this up is too complicated.


Juergen