From: "Alex Bennée" <alex.bennee@linaro.org>
To: Alistair Francis <alistair23@gmail.com>
Cc: "Peter Maydell" <peter.maydell@linaro.org>,
"Thomas Huth" <thuth@redhat.com>,
"Daniel P. Berrangé" <berrange@redhat.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
"QEMU Developers" <qemu-devel@nongnu.org>,
qemu-discuss <qemu-discuss@nongnu.org>,
"Christian Borntraeger" <borntraeger@de.ibm.com>,
qemu-s390x <qemu-s390x@nongnu.org>,
qemu-arm <qemu-arm@nongnu.org>,
"open list:New World" <qemu-ppc@nongnu.org>,
"open list:RISC-V" <qemu-riscv@nongnu.org>
Subject: Re: [RFC PATCH] configure: deprecate 32 bit build hosts
Date: Thu, 26 Sep 2019 20:02:48 +0100 [thread overview]
Message-ID: <878sqaanjb.fsf@linaro.org> (raw)
In-Reply-To: <CAKmqyKOSyhd5zv0hOa_THCX8g1fxN69NXWxCw0m+=TA+8h0Wug@mail.gmail.com>
Alistair Francis <alistair23@gmail.com> writes:
> On Thu, Sep 26, 2019 at 8:41 AM Alex Bennée <alex.bennee@linaro.org> wrote:
>>
>>
>> Thomas Huth <thuth@redhat.com> writes:
>>
>> > On 26/09/2019 15.46, Christian Borntraeger wrote:
>> >>
>> >>
>> >> On 26.09.19 14:58, Daniel P. Berrangé wrote:
>> >>> On Thu, Sep 26, 2019 at 08:50:36AM +0100, Peter Maydell wrote:
>> >>>> On Thu, 26 Sep 2019 at 00:31, Alex Bennée <alex.bennee@linaro.org> wrote:
>> >>>>>
>> >>>>> The 32 bit hosts are already a second class citizen especially with
>> >>>>> support for running 64 bit guests under TCG. We are also limited by
>> >>>>> testing as actual working 32 bit machines are getting quite rare in
>> >>>>> developers personal menageries. For TCG supporting newer types like
>> >>>>> Int128 is a lot harder with 32 bit calling conventions compared to
>> >>>>> their larger bit sized cousins. Fundamentally address space is the
>> >>>>> most useful thing for the translator to have even for a 32 bit guest a
>> >>>>> 32 bit host is quite constrained.
>> >>>>>
>> >>>>> As far as I'm aware 32 bit KVM users are even less numerous. Even
>> >>>>> ILP32 doesn't make much sense given the address space QEMU needs to
>> >>>>> manage.
>> >>>>
>> >>>> For KVM we should wait until the kernel chooses to drop support,
>> >>>> I think.
>> >>>
>> >>> What if the kernel is waiting for QEMU to drop support too ;-P
>> >>
>> >> For what its worth on kvm/s390 we never cared about implementing
>> >> 32 bit.
>> >
>> > Looking at tcg/s390/tcg-target.inc.c :
>> >
>> > ...
>> > /* We only support generating code for 64-bit mode. */
>> > #if TCG_TARGET_REG_BITS != 64
>> > #error "unsupported code generation mode"
>> > #endif
>> > ...
>> >
>> > ... it seems to me that TCG does not support 32-bit on s390 either. I
>> > think we can remove s390 (32-bit) from the list completely?
>>
>> It's the same for riscv32 I think.
>
> I think riscv32 host *should* work, although I don't think it was ever
> tested.
You certainly don't support oversized guests:
/* We don't support oversize guests */
QEMU_BUILD_BUG_ON(TCG_TARGET_REG_BITS < TARGET_LONG_BITS);
>
> Considering that we have enough trouble keeping the riscv32 kernel
> booting it's probably ok to drop it from QEMU.
>
> Alistair
>
>>
>> >
>> > Thomas
>>
>>
>> --
>> Alex Bennée
>>
--
Alex Bennée
next prev parent reply other threads:[~2019-09-26 19:33 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-25 23:30 [RFC PATCH] configure: deprecate 32 bit build hosts Alex Bennée
2019-09-26 7:29 ` Philippe Mathieu-Daudé
2019-09-26 7:50 ` Peter Maydell
2019-09-26 12:58 ` Daniel P. Berrangé
2019-09-26 13:46 ` Christian Borntraeger
2019-09-26 14:26 ` Thomas Huth
2019-09-26 15:27 ` Alex Bennée
2019-09-26 16:11 ` Alistair Francis
2019-09-26 19:02 ` Alex Bennée [this message]
2019-09-27 8:55 ` Gerd Hoffmann
2019-09-26 15:31 ` Alex Bennée
2019-09-26 17:11 ` Richard Henderson
2019-09-30 9:25 ` Daniel P. Berrangé
[not found] ` <87impakrky.fsf@linaro.org>
2019-09-30 10:36 ` Peter Maydell
2019-09-30 11:41 ` Peter Maydell
2019-10-01 17:56 ` Mark Cave-Ayland
2019-10-01 18:02 ` Richard Henderson
2019-10-02 9:10 ` Daniel P. Berrangé
2019-10-02 15:16 ` Richard Henderson
2019-09-26 7:55 ` Thomas Huth
2019-09-26 15:27 ` Alex Bennée
2019-09-27 10:42 ` Mark Cave-Ayland
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