linux-kernel - Re: [PATCH 1/4] sparc: fix accurate exception reporting in copy_{from_to}

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Message-ID: <05acb1676ddc1881e2b9b3fa82f1335c42c2f47e.camel@physik.fu-berlin.de>
Date: Fri, 29 Aug 2025 12:53:33 +0200
From: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To: Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>, 
	linux-kernel@...r.kernel.org
Cc: sparclinux@...r.kernel.org, Andreas Larsson <andreas@...sler.com>, 
 Anthony Yznaga <anthony.yznaga@...cle.com>
Subject: Re: [PATCH 1/4] sparc: fix accurate exception reporting in
 copy_{from_to}_user for UltraSPARC

Hello,

On Tue, 2025-08-26 at 18:03 +0200, Michael Karcher wrote:
> Fixes: cb736fdbb208 ("sparc64: Convert U1copy_{from,to}_user to accurate exception reporting.")
> Signed-off-by: Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>
> ---
>  arch/sparc/lib/U1memcpy.S | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/sparc/lib/U1memcpy.S b/arch/sparc/lib/U1memcpy.S
> index 635398ec7540..154fbd35400c 100644
> --- a/arch/sparc/lib/U1memcpy.S
> +++ b/arch/sparc/lib/U1memcpy.S
> @@ -164,17 +164,18 @@ ENTRY(U1_gs_40_fp)
>  	retl
>  	 add		%o0, %o2, %o0
>  ENDPROC(U1_gs_40_fp)
> -ENTRY(U1_g3_0_fp)
> -	VISExitHalf
> -	retl
> -	 add		%g3, %o2, %o0
> -ENDPROC(U1_g3_0_fp)
>  ENTRY(U1_g3_8_fp)
>  	VISExitHalf
>  	add		%g3, 8, %g3
>  	retl
>  	 add		%g3, %o2, %o0
>  ENDPROC(U1_g3_8_fp)
> +ENTRY(U1_g3_16_fp)
> +	VISExitHalf
> +	add		%g3, 16, %g3
> +	retl
> +	 add		%g3, %o2, %o0
> +ENDPROC(U1_g3_16_fp)
>  ENTRY(U1_o2_0_fp)
>  	VISExitHalf
>  	retl
> @@ -547,18 +548,18 @@ FUNC_NAME:		/* %o0=dst, %o1=src, %o2=len */
>  62:	FINISH_VISCHUNK(o0, f44, f46)
>  63:	UNEVEN_VISCHUNK_LAST(o0, f46, f0)
>  
> -93:	EX_LD_FP(LOAD(ldd, %o1, %f2), U1_g3_0_fp)
> +93:	EX_LD_FP(LOAD(ldd, %o1, %f2), U1_g3_8_fp)
>  	add		%o1, 8, %o1
>  	subcc		%g3, 8, %g3
>  	faligndata	%f0, %f2, %f8
> -	EX_ST_FP(STORE(std, %f8, %o0), U1_g3_8_fp)
> +	EX_ST_FP(STORE(std, %f8, %o0), U1_g3_16_fp)
>  	bl,pn		%xcc, 95f
>  	 add		%o0, 8, %o0
> -	EX_LD_FP(LOAD(ldd, %o1, %f0), U1_g3_0_fp)
> +	EX_LD_FP(LOAD(ldd, %o1, %f0), U1_g3_8_fp)
>  	add		%o1, 8, %o1
>  	subcc		%g3, 8, %g3
>  	faligndata	%f2, %f0, %f8
> -	EX_ST_FP(STORE(std, %f8, %o0), U1_g3_8_fp)
> +	EX_ST_FP(STORE(std, %f8, %o0), U1_g3_16_fp)
>  	bge,pt		%xcc, 93b
>  	 add		%o0, 8, %o0
>  

Verified to work on QEMU which emulates an UltraSPARC II:

root@...ian:~# cat /proc/cpuinfo 
cpu             : TI UltraSparc IIi (Sabre)
fpu             : UltraSparc IIi integrated FPU
pmu             : ultra12
prom            : OBP 3.10.24 1999/01/01 01:01
type            : sun4u
ncpus probed    : 1
ncpus active    : 1
D$ parity tl1   : 0
I$ parity tl1   : 0
cpucaps         : flush,stbar,swap,muldiv,v9,mul32,div32,v8plus,vis
Cpu0ClkTck      : 0000000005f5e100
MMU Type        : Spitfire
MMU PGSZs       : 8K,64K,512K,4MB
State:
CPU0:           online
root@...ian:~# 

While there were no obvious problems on UltraSPARC before, these may show after several
days of uptime, similar to Niagara 4. I remember though that there were user reports of
unstable kernels on real UltraSPARC I and II machines.

Tested-by: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
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