qemu-devel.nongnu.org archive mirror
 help / color / mirror / Atom feed
From: "Keith Packard" <keithp@keithp.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: "Alex Bennée" <alex.bennee@linaro.org>,
	"QEMU Developers" <qemu-devel@nongnu.org>
Subject: Re: [PATCH] Semihost SYS_READC implementation (v4)
Date: Fri, 25 Oct 2019 12:15:45 -0700	[thread overview]
Message-ID: <87mudo4owu.fsf@keithp.com> (raw)
In-Reply-To: <CAFEAcA-g+RkvYjseDE=1Z=gnLum0Cjvn_7bqB3ti+cBq9UZ3Eg@mail.gmail.com>

[-- Attachment #1: Type: text/plain, Size: 1532 bytes --]

Peter Maydell <peter.maydell@linaro.org> writes:

> Is there a specification for RISC-V semihosting? This is
> likely to be my first question when the support comes
> round for review, so you can have it early :-)  We'd
> prefer to implement specified interfaces, not random
> ad-hoc "this seems to be what newlib wants to see,
> which is turn got hacked together by copying some other
> architecture's code".

There seems to be convergence on a pretty simple interface which uses
ebreak surrounded by a couple of specific no-ops:

      slli x0, x0, 0x1f
      ebreak
      srai x0, x0, 0x7

There are implementations in rust and openocd, and I've got one for
picolibc. The risc-v semihosting code is sitting on a branch in my repo
on github:

        https://github.com/keith-packard/qemu/tree/riscv-semihost

> (describing a mechanism to avoid stopping the emulator)
> This feels to me like it's a bit overcomplicated unless it turns out
> we actually require it though.

Would also be nice for multi-core setups. I'd like to start with the
simple plan for now.

> Isn't the answer to this "don't use a command line that tries
> to connect stdio to multiple things" ?

Uh, we do that all the time? The mux device is designed to handle this
so that you can use stdio for both monitor commands and application
I/O. It's very convenient, the only issue is that the last device that
hooks to the mux ends up getting input first (you use ^Ac to rotate
among the selected devices).

-- 
-keith

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 832 bytes --]

  reply	other threads:[~2019-10-25 19:18 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-23 19:26 [PATCH] Semihost SYS_READC implementation (v3) Keith Packard
2019-10-24 17:33 ` no-reply
2019-10-24 18:54   ` Paolo Bonzini
2019-10-24 22:46     ` [PATCH] Semihost SYS_READC implementation (v4) Keith Packard
2019-10-25  9:51       ` Alex Bennée
2019-10-25 16:36         ` Keith Packard
2019-10-25 16:49           ` Peter Maydell
2019-10-25 19:15             ` Keith Packard [this message]
2019-10-25 20:53               ` Peter Maydell
2019-10-25 23:18                 ` Keith Packard
2019-11-04 20:42                   ` [PATCH] Semihost SYS_READC implementation (v6) Keith Packard
2019-12-17  8:38                     ` Alex Bennée
2019-12-17  9:08                       ` Paolo Bonzini
2019-12-17  9:51                         ` Alex Bennée
2019-12-17 10:04                           ` Paolo Bonzini
2019-12-17 12:14                             ` [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP) Alex Bennée
2019-12-17 12:22                               ` Paolo Bonzini
2019-12-17 13:42                                 ` Alex Bennée
2019-12-17 13:48                                   ` Paolo Bonzini
2019-12-17 14:18                                     ` Alex Bennée
2019-12-17 14:39                                       ` Paolo Bonzini
2019-12-17 14:39                                       ` Paolo Bonzini
2019-12-18 17:36                                         ` Alex Bennée
2019-12-18 21:23                                           ` Paolo Bonzini
2019-11-05  5:10                 ` [PATCH] Semihost SYS_READC implementation (v4) Keith Packard
2019-11-11 14:51                   ` Peter Maydell
2019-11-14 15:46                     ` Alistair Francis
2019-11-14 17:43                       ` Keith Packard
2019-11-14 17:39                     ` Keith Packard
2019-11-14 17:47                       ` Peter Maydell
2019-11-14 19:20                         ` Peter Maydell
2019-11-14 16:14               ` Peter Maydell
2019-11-14 18:05                 ` Keith Packard
2019-11-14 18:18                   ` Peter Maydell
2019-11-14 19:18                 ` Richard Henderson
2019-11-14 19:29                   ` Peter Maydell
2019-11-14 20:52                     ` Richard Henderson
2019-11-14 21:04                       ` Peter Maydell
2019-11-14 22:26                   ` Keith Packard
2019-11-15 10:54                     ` Peter Maydell
2019-11-15 23:40                       ` Keith Packard
2019-10-25 17:02           ` Alex Bennée
2019-10-25 18:17       ` no-reply
2019-10-25 18:20       ` no-reply
2019-10-24 17:43 ` [PATCH] Semihost SYS_READC implementation (v3) no-reply

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=87mudo4owu.fsf@keithp.com \
    --to=keithp@keithp.com \
    --cc=alex.bennee@linaro.org \
    --cc=peter.maydell@linaro.org \
    --cc=qemu-devel@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).