From: "Maciej W. Rozycki" <macro@linux-mips.org>
To: Fredrik Noring <noring@nocrew.org>
Cc: "Aleksandar Markovic" <amarkovic@wavecomp.com>,
"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Aurelien Jarno" <aurelien@aurel32.net>,
"qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>,
"Jürgen Urban" <JuergenUrban@gmx.de>
Subject: Re: [Qemu-devel] [PATCH] target/mips: Support Toshiba specific three-operand MADD and MADDU
Date: Tue, 16 Oct 2018 19:55:45 +0100 (BST) [thread overview]
Message-ID: <alpine.LFD.2.21.1810161947360.16498@eddie.linux-mips.org> (raw)
In-Reply-To: <20181016181916.GB2323@sx9>
On Tue, 16 Oct 2018, Fredrik Noring wrote:
> One option is to create a new array such as
>
> static TCGv_i64 mmi_gpr[32];
>
> that represents the upper 64 bits of each GPR. Then cpu_gpr must be of
> a 64-bit type too, even when QEMU runs in 32-bit user mode. The R5900
> does not implement CP0.Status.UX in hardware, though, so system mode is
> 64 bits, regardless.
It's more like modern CP0.Status.PX however, as the hardware does not
implement 64-bit memory segments and only has legacy 32-bit segments
implemented.
Due to a hardware quirk however the value recorded in the target register
(usually $ra) does not get sign-extended with linked jump or branch
instructions, contrary to what is expected with processors implementing
32-bit segments only. This has implications for kernel code running from
KSEG0/KSEG1/KSEG2 and has to be worked around in software, as experience
has shown.
Maciej
next prev parent reply other threads:[~2018-10-16 18:55 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-14 14:29 [Qemu-devel] [PATCH] target/mips: Support Toshiba specific three-operand MADD and MADDU Philippe Mathieu-Daudé
2018-10-14 16:41 ` Fredrik Noring
2018-10-14 21:56 ` Philippe Mathieu-Daudé
2018-10-14 23:03 ` Maciej W. Rozycki
2018-10-15 17:02 ` Fredrik Noring
2018-10-16 9:43 ` Aleksandar Markovic
2018-10-16 18:19 ` Fredrik Noring
2018-10-16 18:37 ` Richard Henderson
2018-10-16 18:52 ` Fredrik Noring
2018-10-16 19:02 ` Maciej W. Rozycki
2018-10-19 18:09 ` Aleksandar Markovic
2018-10-28 19:43 ` Aleksandar Markovic
2018-10-28 20:00 ` Maciej W. Rozycki
2018-10-29 11:52 ` Aleksandar Markovic
2018-10-29 14:51 ` Fredrik Noring
2018-10-29 15:03 ` Aleksandar Markovic
2018-10-29 15:44 ` Maciej W. Rozycki
2018-10-16 18:55 ` Maciej W. Rozycki [this message]
2018-10-15 15:36 ` Fredrik Noring
2018-10-24 18:01 ` Fredrik Noring
2018-10-26 11:17 ` Aleksandar Markovic
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