From: Peter Maydell <peter.maydell@linaro.org>
To: Thomas Huth <thuth@redhat.com>
Cc: "Auger Eric" <eric.auger@redhat.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
qemu-arm <qemu-arm@nongnu.org>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>,
"QEMU Developers" <qemu-devel@nongnu.org>
Subject: Re: [PATCH 2/4] target/arm: Move cortex-m related functions to new file v7m.c
Date: Mon, 23 Sep 2019 19:45:57 +0100 [thread overview]
Message-ID: <CAFEAcA9k59CRG23qP-o5PF0mdXvXpszhuxx+GpbpWO+hFdHOOA@mail.gmail.com> (raw)
In-Reply-To: <8585b93b-e239-829b-d634-b89941f27aed@redhat.com>
On Mon, 23 Sep 2019 at 19:09, Thomas Huth <thuth@redhat.com> wrote:
> However, there's one thing I currently don't quite understand in this
> code (since I'm not an ARM guy, sorry) : There are references to "v8" in
> m_helper.c, too. Is that related to a separate CPU type, ie. should the
> v8 code also be available when CONFIG_ARM_V7M is disabled? Or can the
> code in m_helper.c be disabled completely if CONFIG_ARM_V7M is not set?
QEMU's naming conventions here is a bit confusing, for
historical reasons.
Architecturally what we have is:
* "M-profile" -- this is the flavour of Arm architecture for
microcontrollers; it has some big differences from A and R
profile (eg the exception mechanism is different and it has
a built-in NVIC interrupt controller). All the Cortex-M<anything>
CPUs are M-profile
* "Arm-v7M" -- this is the v7 flavour of the M-profile
architecture, eg Cortex-M3.
* "Arm-v6M" -- this looks like it ought to mean "v6 flavour
of M-profile", but if you look at what features it has it's
more like "cut down version of v7M" (fewer instructions, cut
down exception model, etc, but some things which on A-profile
don't appear until v7A are present in v6M). Cortex-M0 and -M1.
* "Arm-v8M" -- v8 flavour of M-profile. The big change here
is support for TrustZone. Cortex-M33. v8M comes in two
sub-profiles: "mainline", which has all the features like v7M,
and "baseline", which is cut-down in the same way v6M is a
cut-down v7M.
In QEMU, we implemented Cortex-M3 first, and then added -M0 and
-M33 later. So mostly our function naming convention uses
"v7m" when it means "any M-profile"; a few v8M-specific
functions use a "v8m" prefix. Everything in m_helper.c is
M-profile specific; most of it is used by all M-profile cores,
and a few bits are v8M-only or v7M-and-v8M-mainline only.
From a CONFIG switch point of view I don't think it's
worth being able to #ifdef out the various flavours of
M-profile individually.
thanks
-- PMM
next prev parent reply other threads:[~2019-09-23 18:48 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-21 15:04 [PATCH 0/4] Make it possible to compile with CONFIG_ARM_V7M=n Thomas Huth
2019-09-21 15:04 ` [PATCH 1/4] target/arm: Make cpu_register() and set_feature() available for other files Thomas Huth
2019-09-23 14:28 ` Auger Eric
2019-09-21 15:04 ` [PATCH 2/4] target/arm: Move cortex-m related functions to new file v7m.c Thomas Huth
2019-09-23 14:31 ` Auger Eric
2019-09-23 18:09 ` Thomas Huth
2019-09-23 18:45 ` Peter Maydell [this message]
2019-09-23 18:51 ` Thomas Huth
2019-09-23 18:54 ` Peter Maydell
2019-09-24 11:02 ` Auger Eric
2019-09-24 11:06 ` Thomas Huth
2019-09-24 11:24 ` Auger Eric
2019-09-23 14:34 ` Peter Maydell
2019-09-24 9:52 ` Philippe Mathieu-Daudé
2019-09-21 15:04 ` [PATCH 3/4] hw/arm: Move armv7m_nvic.c to hw/arm/ and always enable it for arm builds Thomas Huth
2019-09-23 14:52 ` Peter Maydell
2019-09-23 17:54 ` Thomas Huth
2019-09-23 18:27 ` Peter Maydell
2019-09-23 18:36 ` Thomas Huth
2019-09-23 18:50 ` Peter Maydell
2019-09-24 4:44 ` Thomas Huth
2019-09-24 9:42 ` Peter Maydell
2019-09-24 9:48 ` Thomas Huth
2019-09-24 10:01 ` Philippe Mathieu-Daudé
2019-09-21 15:04 ` [PATCH 4/4] default-configs: Do not enforce CONFIG_ARM_V7M anymore Thomas Huth
2019-09-23 8:37 ` [PATCH 0/4] Make it possible to compile with CONFIG_ARM_V7M=n Philippe Mathieu-Daudé
2019-09-23 8:50 ` Thomas Huth
2019-09-23 8:58 ` Philippe Mathieu-Daudé
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