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Re: Deprecate 32-bit hosts? (was: Re: [PULL 14/14] hw/arm/aspeed: Add Fu
From: |
Daniel P . Berrangé |
Subject: |
Re: Deprecate 32-bit hosts? (was: Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type) |
Date: |
Wed, 15 Sep 2021 10:05:11 +0100 |
User-agent: |
Mutt/2.0.7 (2021-05-04) |
On Wed, Sep 15, 2021 at 10:51:56AM +0200, Philippe Mathieu-Daudé wrote:
> On 9/15/21 10:37 AM, Daniel P. Berrangé wrote:
> > On Wed, Sep 15, 2021 at 09:42:48AM +0200, Thomas Huth wrote:
> >> On 14/09/2021 17.22, Richard Henderson wrote:
> >>> On 9/14/21 5:26 AM, Peter Maydell wrote:
> >>>> (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)
> >>>
> >>> Recalling that the win64 abi model is p64, i.e. 'long' is still 32-bit
> >>> while pointers are 64-bit, how close do we think we are to this being
> >>> fixed already?
> >>>
> >>>> 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.
> >>>
> >>> I'm not opposed to deprecating 32-bit hosts... ;-)
> >>
> >> I think we should consider this again, indeed. Plain 32-bit CPUs are quite
> >> seldom these days, aren't they? And I think we urgently need to decrease
> >> the
> >> amount of things that we have to test and maintain in our CI and developer
> >> branches... So is there still a really really compelling reason to keep
> >> 32-bit host support alive?
> >
> > I think it probably depends on the architecture to some extent.
> >
> > i386 is possibly getting rare enough to consider dropping, though
> > IIUC, KVM in the kernel still supports it. Would feel odd to drop
> > it in QEMU if the kernel still thinks it is popular enough to keep
> > KVM support.
> >
> > armv7 feels like it is relatively common as 64-bit didn't arrive
> > in widespread use until relatively recent times compared to x86_64.
> > KVM dropped armv7, but then hardware for that was never widespread,
> > so armv7 was always TCG dominated
> >
> > Other 32-bit arches were/are always rare.
>
> While I could understand there are rare uses of system emulation on
> 32-bit hosts, I still believe user-emulation is used, but would like
> to be proven to the contrary. With that in mind, I'm not sure removing
> sysemu on 32-bit hosts is worthful. Maybe we should ask distribution
> maintainers first, then eventually poll the community? Or start with
> a deprecation warning?
Well Debian still supports arm7, i686, mips officially, and several
more unofficially, so that's an easy answer from that side.
Fedora only has arm7, having dropped i686 a while ago.
I don't have insight into usage of QEMU on any platforms breakdown
though.
Regards,
Daniel
--
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- [PULL 14/14] hw/arm/aspeed: Add Fuji machine type, (continued)
- [PULL 14/14] hw/arm/aspeed: Add Fuji machine type, Cédric Le Goater, 2021/09/13
- Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type, Cédric Le Goater, 2021/09/14
- Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type, Peter Delevoryas, 2021/09/14
- Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type, Joel Stanley, 2021/09/14
- Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type, Peter Maydell, 2021/09/14
- Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type, Richard Henderson, 2021/09/14
- Deprecate 32-bit hosts? (was: Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type), Thomas Huth, 2021/09/15
- Re: Deprecate 32-bit hosts? (was: Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type), Philippe Mathieu-Daudé, 2021/09/15
- Re: Deprecate 32-bit hosts? (was: Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type), Daniel P . Berrangé, 2021/09/15
- Re: Deprecate 32-bit hosts? (was: Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type), Philippe Mathieu-Daudé, 2021/09/15
- Re: Deprecate 32-bit hosts? (was: Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type),
Daniel P . Berrangé <=
- Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type, Cédric Le Goater, 2021/09/16
- Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type, Philippe Mathieu-Daudé, 2021/09/16
- Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type, Cédric Le Goater, 2021/09/16
- Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type, Peter Maydell, 2021/09/16
[PULL 05/14] hw: aspeed_gpio: Simplify 1.8V defines, Cédric Le Goater, 2021/09/13
[PULL 12/14] hw/arm/aspeed: Initialize AST2600 UART clock selection registers, Cédric Le Goater, 2021/09/13
[PULL 06/14] hw: aspeed_gpio: Clarify GPIO controller name, Cédric Le Goater, 2021/09/13
[PULL 09/14] aspeed: Emulate the AST2600A3, Cédric Le Goater, 2021/09/13
[PULL 13/14] hw/arm/aspeed: Allow machine to set UART default, Cédric Le Goater, 2021/09/13
[PULL 02/14] hw: arm: aspeed: Enable mac0/1 instead of mac1/2 for g220a, Cédric Le Goater, 2021/09/13