From: Alistair Francis <alistair23@gmail.com>
To: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
"open list:RISC-V" <qemu-riscv@nongnu.org>,
"qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>,
Atish Patra <Atish.Patra@wdc.com>
Subject: Re: [Qemu-devel] [PATCH for 4.1] RISC-V: Ignore the S and U extensions when formatting ISA strings
Date: Wed, 7 Aug 2019 10:54:52 -0700 [thread overview]
Message-ID: <CAKmqyKMKBsHO2QCYC1qeGTQa0cUMEpke17dgkB=hgQC-Nd9upw@mail.gmail.com> (raw)
In-Reply-To: <20190807145939.1281-1-palmer@sifive.com>
On Wed, Aug 7, 2019 at 8:00 AM Palmer Dabbelt <palmer@sifive.com> wrote:
>
> The ISA strings we're providing from QEMU aren't actually legal RISC-V
> ISA strings, as both the S and U extensions cannot exist as
> single-letter extensions and must instead be multi-letter strings.
> We're still using the ISA strings inside QEMU to track the availiable
s/availiable/available/g
> extensions, so this patch just strips out the S and U extensions when
> formatting ISA strings.
Atish and I were talking about this and we concluded that S and U
aren't extensions, but should be reported in the misa CSR.
>
> This boots Linux on top of 4.1-rc3, which no longer has the U extension
> in /proc/cpuinfo.
>
> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
> ---
> This is another late one, but I'd like to target it for 4.1 as we're
> providing illegal ISA strings and I don't want to bake that into a bunch
> of other code.
> ---
> target/riscv/cpu.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index f8d07bd20ad7..4df14433d789 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -501,7 +501,22 @@ char *riscv_isa_string(RISCVCPU *cpu)
> char *p = isa_str + snprintf(isa_str, maxlen, "rv%d", TARGET_LONG_BITS);
> for (i = 0; i < sizeof(riscv_exts); i++) {
> if (cpu->env.misa & RV(riscv_exts[i])) {
> - *p++ = qemu_tolower(riscv_exts[i]);
> + char lower = qemu_tolower(riscv_exts[i]);
> + switch (lower) {
> + case 's':
> + case 'u':
> + /*
> + * The 's' and 'u' extensions shouldn't be passed in the device
> + * tree, but we still use them internally to track extension
> + * sets. Here we just explicitly remove them when formatting
> + * an ISA string.
This should be updated to note mention 's' and 'u' as extensions, but
clarify that they are correctly include in the misa CSR.
Alistair
> + */
> + break;
> +
> + default:
> + *p++ = qemu_tolower(riscv_exts[i]);
> + break;
> + }
> }
> }
> *p = '\0';
> --
> 2.21.0
>
>
next prev parent reply other threads:[~2019-08-07 17:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-07 14:59 [Qemu-devel] [PATCH for 4.1] RISC-V: Ignore the S and U extensions when formatting ISA strings Palmer Dabbelt
2019-08-07 15:27 ` Paul Walmsley
2019-08-07 16:08 ` Peter Maydell
2019-08-07 16:20 ` Palmer Dabbelt
2019-08-07 16:41 ` Peter Maydell
2019-08-07 17:25 ` Palmer Dabbelt
2019-08-07 17:54 ` Alistair Francis [this message]
2019-08-13 22:54 ` Palmer Dabbelt
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAKmqyKMKBsHO2QCYC1qeGTQa0cUMEpke17dgkB=hgQC-Nd9upw@mail.gmail.com' \
--to=alistair23@gmail.com \
--cc=Alistair.Francis@wdc.com \
--cc=Atish.Patra@wdc.com \
--cc=palmer@sifive.com \
--cc=paul.walmsley@sifive.com \
--cc=qemu-devel@nongnu.org \
--cc=qemu-riscv@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).