linux-kernel - Re: [PATCH] powerpc/8xx: Reduce time spent in allow_user

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Date:   Tue,  9 Jun 2020 15:28:36 +1000 (AEST)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@....fr>,
        Paul Mackerras <paulus@...ba.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/8xx: Reduce time spent in allow_user_access() and friends

On Wed, 15 Apr 2020 10:06:09 +0000 (UTC), Christophe Leroy wrote:
> To enable/disable kernel access to user space, the 8xx has to
> modify the properties of access group 1. This is done by writing
> predefined values into SPRN_Mx_AP registers.
> 
> As of today, a __put_user() gives:
> 
> 00000d64 <my_test>:
>  d64:	3d 20 4f ff 	lis     r9,20479
>  d68:	61 29 ff ff 	ori     r9,r9,65535
>  d6c:	7d 3a c3 a6 	mtspr   794,r9
>  d70:	39 20 00 00 	li      r9,0
>  d74:	90 83 00 00 	stw     r4,0(r3)
>  d78:	3d 20 6f ff 	lis     r9,28671
>  d7c:	61 29 ff ff 	ori     r9,r9,65535
>  d80:	7d 3a c3 a6 	mtspr   794,r9
>  d84:	4e 80 00 20 	blr
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/8xx: Reduce time spent in allow_user_access() and friends
      https://git.kernel.org/powerpc/c/332ce969b763553e9c4d55069e1e15aba4ea560f

cheers