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From: Peter Maydell <peter.maydell@linaro.org>
To: Joel Stanley <joel@jms.id.au>
Cc: "Andrew Jeffery" <andrew@aj.id.au>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	"qemu-arm@nongnu.org" <qemu-arm@nongnu.org>,
	"Cédric Le Goater" <clg@kaod.org>,
	"Peter Delevoryas" <pdel@fb.com>
Subject: Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type
Date: Tue, 14 Sep 2021 13:26:01 +0100	[thread overview]
Message-ID: <CAFEAcA8ntPE3GkTNU8bSBhCWzk_jdH4QR1kDgwo6deQ+T1iOKw@mail.gmail.com> (raw)
In-Reply-To: <CACPK8Xdey9_x-ZN1JbgFyTrW59EapH4xcqYbyNQxyQ5t0uWPvw@mail.gmail.com>

On Tue, 14 Sept 2021 at 13:14, Joel Stanley <joel@jms.id.au> wrote:
> The upstream device tree uses 2G:
>
> https://elixir.bootlin.com/linux/v5.15-rc1/source/arch/arm/boot/dts/ast2600-facebook-netbmc-common.dtsi#L20
>
> It's unfortunate we limit the defaults given very few (no one?) is
> using this model on a machine that is 32 bit.

This runs into a set of desires which are all reasonable
but unfortunately sometimes in conflict:

(1) boards should behave the same on all hosts (whether those
    hosts are 64 bit or 32 bit)
(2) RAM blocks should have a length that fits inside a
    signed 32-bit type on 32-bit hosts (at least I assume this
    is where the 2047MB limit is coming from; in theory this ought
    to be improveable but auditing the code for mishandling of
    RAMblock sizes to ensure we weren't accidentally stuffing
    their size into a signed 'long' somewhere would be kind
    of painful)
(3) default behaviour of a board should match the real
    hardware
(4) every board should start cleanly with no non-default
    arguments, so we can have a machine-model agnostic test
    of "does every machine we support at least init cleanly"

So far when we have run into this problem with other machine
types, the one that we have ended up discarding is (3).

There's a good argument to be made that what we should deal
with is (2) -- this probably involves making ram_addr_t
be 64-bits always, rather than "64 bits unless we're on
a 32-bit host and Xen is not compiled in", and a certain
amount of testing or audit that we don't have any places
where we stuff ram sizes into 'long' variables. But it's a lot
more work than compromising on (3) :-)

Even if we did fix (2) we'd need to compromise on (3)
sometimes still -- if a board has 4GB of RAM that's
not going to fit in 32 bits regardless. But we would be
able to let boards with 2GB have 2GB.

thanks
-- PMM


  reply	other threads:[~2021-09-14 12:40 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-13 16:12 [PULL 00/14] aspeed queue Cédric Le Goater
2021-09-13 16:12 ` [PULL 01/14] hw: arm: aspeed: Enable eth0 interface for aspeed-ast2600-evb Cédric Le Goater
2021-09-13 16:12 ` [PULL 02/14] hw: arm: aspeed: Enable mac0/1 instead of mac1/2 for g220a Cédric Le Goater
2021-09-13 16:12 ` [PULL 03/14] watchdog: aspeed: Sanitize control register values Cédric Le Goater
2021-09-13 16:12 ` [PULL 04/14] watchdog: aspeed: Fix sequential control writes Cédric Le Goater
2021-09-13 16:12 ` [PULL 05/14] hw: aspeed_gpio: Simplify 1.8V defines Cédric Le Goater
2021-09-13 16:12 ` [PULL 06/14] hw: aspeed_gpio: Clarify GPIO controller name Cédric Le Goater
2021-09-13 16:12 ` [PULL 07/14] misc/pca9552: Fix LED status register indexing in pca955x_get_led() Cédric Le Goater
2021-09-13 16:12 ` [PULL 08/14] arm/aspeed: rainier: Add i2c eeproms and muxes Cédric Le Goater
2021-09-13 16:12 ` [PULL 09/14] aspeed: Emulate the AST2600A3 Cédric Le Goater
2021-09-13 16:13 ` [PULL 10/14] hw/misc: Add Infineon DPS310 sensor model Cédric Le Goater
2021-09-13 16:13 ` [PULL 11/14] arm/aspeed: Add DPS310 to Witherspoon and Rainier Cédric Le Goater
2021-09-13 16:13 ` [PULL 12/14] hw/arm/aspeed: Initialize AST2600 UART clock selection registers Cédric Le Goater
2021-09-13 16:13 ` [PULL 13/14] hw/arm/aspeed: Allow machine to set UART default Cédric Le Goater
2021-09-13 16:13 ` [PULL 14/14] hw/arm/aspeed: Add Fuji machine type Cédric Le Goater
2021-09-14 10:56   ` Cédric Le Goater
2021-09-14 11:59     ` Peter Delevoryas
2021-09-14 12:14       ` Joel Stanley
2021-09-14 12:26         ` Peter Maydell [this message]
2021-09-14 15:22           ` Richard Henderson
2021-09-15  7:42             ` Deprecate 32-bit hosts? (was: Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type) Thomas Huth
2021-09-15  7:54               ` Philippe Mathieu-Daudé
2021-09-15  8:37               ` Daniel P. Berrangé
2021-09-15  8:51                 ` Philippe Mathieu-Daudé
2021-09-15  9:05                   ` Daniel P. Berrangé
2021-09-16 12:29             ` [PULL 14/14] hw/arm/aspeed: Add Fuji machine type Cédric Le Goater
2021-09-16 13:53               ` Philippe Mathieu-Daudé
2021-09-16 14:06                 ` Cédric Le Goater
2021-09-16 14:07                   ` Peter Maydell
2021-09-14 10:51 ` [PULL 00/14] aspeed queue Peter Maydell
2021-09-14 10:58   ` Cédric Le Goater
2021-09-14 11:38     ` Philippe Mathieu-Daudé
  -- strict thread matches above, loose matches on Subject: below --
2021-09-20  8:09 Cédric Le Goater
2021-09-20  8:09 ` [PULL 14/14] hw/arm/aspeed: Add Fuji machine type Cédric Le Goater
2021-09-03 19:40 [PULL 00/14] aspeed queue Cédric Le Goater
2021-09-03 19:41 ` [PULL 14/14] hw/arm/aspeed: Add Fuji machine type Cédric Le Goater
2021-09-03 20:39   ` Philippe Mathieu-Daudé

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