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From: "Maciej W. Rozycki" <macro@linux-mips.org>
To: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
Cc: "Fredrik Noring" <noring@nocrew.org>,
	"Mathieu Malaterre" <malat@debian.org>,
	"Richard Henderson" <richard.henderson@linaro.org>,
	qemu-devel@nongnu.org, "Laurent Vivier" <laurent@vivier.eu>,
	"YunQiang Su" <wzssyqa@gmail.com>,
	"James Cowgill" <james410@cowgill.org.uk>,
	"David Daney" <ddaney.cavm@gmail.com>,
	"Jürgen Urban" <JuergenUrban@gmx.de>,
	"Aurelien Jarno" <aurelien@aurel32.net>,
	"Richard Henderson" <rth@twiddle.net>
Subject: Re: [PATCH 3/4] default-configs: Support o32 ABI with 64-bit MIPS CPUs
Date: Thu, 19 Nov 2020 16:45:29 +0000 (GMT)	[thread overview]
Message-ID: <alpine.LFD.2.21.2011191634540.656242@eddie.linux-mips.org> (raw)
In-Reply-To: <20201119161710.1985083-4-f4bug@amsat.org>

On Thu, 19 Nov 2020, Philippe Mathieu-Daudé wrote:

> MIPS o32 ABI on 64-bit CPUs looks like a ILP32-on-64bit data
> model, allowing 64-bit arithmetic and data movement instructions.
> 
> This is the default ABI used by the "Sony Linux Toolkit for
> Playstation 2".

 Please don't, not at least with a generic configuration (i.e. make it 
unambiguous that this is R5900-specific).  This only works with R5900 
because it does not implement the MIPS ISA correctly (e.g. see what $ra is 
set to with JAL/JALR/etc. in the kernel mode), and it is not supported by 
the standard Linux ABI.  Use n32 instead, which has the same functionality 
and is standard (and is also a better ABI in terms of performance).

 You'd probably need to implement all the R5900 addressing quirks for your 
proposed hack to match hardware, or otherwise you'll end up with emulation 
that creates its own reality.

  Maciej


  reply	other threads:[~2020-11-19 16:47 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-19 16:17 [PATCH 0/4] linux-user: Support o32 ABI with 64-bit MIPS CPUs Philippe Mathieu-Daudé
2020-11-19 16:17 ` [PATCH 1/4] linux-user/mips64: Restore setup_frame() for o32 ABI Philippe Mathieu-Daudé
2020-11-19 23:07   ` Richard Henderson
2020-12-17 10:18   ` Laurent Vivier
2021-02-11 21:33   ` Laurent Vivier
2020-11-19 16:17 ` [PATCH 2/4] linux-user/mips64: Support o32 ABI syscalls Philippe Mathieu-Daudé
2020-11-19 23:08   ` Richard Henderson
2020-11-19 23:09     ` Richard Henderson
2020-12-17 10:40   ` Laurent Vivier
2020-12-17 16:10     ` Philippe Mathieu-Daudé
2020-12-17 17:20       ` Fredrik Noring
2020-12-17 20:14       ` Laurent Vivier
2021-02-11 21:33   ` Laurent Vivier
2020-11-19 16:17 ` [PATCH 3/4] default-configs: Support o32 ABI with 64-bit MIPS CPUs Philippe Mathieu-Daudé
2020-11-19 16:45   ` Maciej W. Rozycki [this message]
2020-11-19 17:13     ` Philippe Mathieu-Daudé
2020-12-12  8:29       ` Fredrik Noring
2020-12-12 17:03     ` Fredrik Noring
2020-11-19 16:17 ` [PATCH 4/4] RFC qemu-binfmt-conf.sh: Add MIPS64 o32 ABI Philippe Mathieu-Daudé
2020-11-19 23:14   ` Richard Henderson
2020-11-19 16:27 ` [PATCH 0/4] linux-user: Support o32 ABI with 64-bit MIPS CPUs no-reply
2020-12-13 15:14 ` Philippe Mathieu-Daudé
2021-02-09 18:31   ` Philippe Mathieu-Daudé

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