From: Richard Henderson <richard.henderson@linaro.org>
To: Michael Clark <mjc@sifive.com>, qemu-devel@nongnu.org
Cc: patches@groups.riscv.org, "Palmer Dabbelt" <palmer@sifive.com>,
"Sagar Karandikar" <sagark@eecs.berkeley.edu>,
"Bastian Koppelmann" <kbastian@mail.uni-paderborn.de>,
"Peter Maydell" <peter.maydell@linaro.org>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Philippe Mathieu-Daudé" <f4bug@amsat.org>
Subject: Re: [Qemu-devel] [PATCH v2 1/1] RISC-V: Workaround for critical mstatus.FS MTTCG bug
Date: Wed, 28 Mar 2018 13:14:45 +0800 [thread overview]
Message-ID: <e2a518fd-34ef-537a-b8b4-efbd8e61ca6a@linaro.org> (raw)
In-Reply-To: <1522197746-26020-2-git-send-email-mjc@sifive.com>
On 03/28/2018 08:42 AM, Michael Clark wrote:
> This change is a workaround for a bug where mstatus.FS
> is not correctly reporting dirty after operations that
> modify floating point registers. This a critical bug
> or RISC-V in QEMU as it results in floating point
> register file corruption when running SMP Linux due to
> task migration and possibly uniprocessor Linux if
> more than one process is using the FPU.
>
> This workaround will return dirty if mstatus.FS is
> switched from off to initial or clean. According to
> the specification it is legal for an implementation
> to return only off, or dirty.
>
> Cc: Palmer Dabbelt <palmer@sifive.com>
> Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
> Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
> Cc: Peter Maydell <peter.maydell@linaro.org>
> Cc: Alex Bennée <alex.bennee@linaro.org>
> Cc: Richard Henderson <richard.henderson@linaro.org>
> Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
> Tested-by: Richard W.M. Jones <rjones@redhat.com>
> Signed-off-by: Michael Clark <mjc@sifive.com>
> ---
> target/riscv/op_helper.c | 17 +++++++++++++++--
> 1 file changed, 15 insertions(+), 2 deletions(-)
In case the more extensive fix waits until 2.13,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
r~
next prev parent reply other threads:[~2018-03-28 5:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-28 0:42 [Qemu-devel] [PATCH v2 0/1] RISC-V: Critical fixes for QEMU 2.12 Michael Clark
2018-03-28 0:42 ` [Qemu-devel] [PATCH v2 1/1] RISC-V: Workaround for critical mstatus.FS MTTCG bug Michael Clark
2018-03-28 5:14 ` Richard Henderson [this message]
2018-03-28 0:42 ` [Qemu-devel] [PATCH v2 1/1] RISC-V: Workaround for critical mstatus.FS bug Michael Clark
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