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Thu, 26 Sep 2019 08:27:49 -0700 (PDT) Received: from zen.linaroharston ([51.148.130.216]) by smtp.gmail.com with ESMTPSA id b186sm9232360wmd.16.2019.09.26.08.27.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Sep 2019 08:27:48 -0700 (PDT) Received: from zen (localhost [127.0.0.1]) by zen.linaroharston (Postfix) with ESMTP id D86A11FF87; Thu, 26 Sep 2019 16:27:47 +0100 (BST) References: <20190925233013.6449-1-alex.bennee@linaro.org> <20190926125817.GB19660@redhat.com> <19efe3ee-a532-cf66-a5a7-03a7c053737c@redhat.com> User-agent: mu4e 1.3.4; emacs 27.0.50 From: Alex =?utf-8?Q?Benn=C3=A9e?= To: Thomas Huth Subject: Re: [RFC PATCH] configure: deprecate 32 bit build hosts In-reply-to: <19efe3ee-a532-cf66-a5a7-03a7c053737c@redhat.com> Date: Thu, 26 Sep 2019 16:27:47 +0100 Message-ID: <87d0fn9ix8.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.85.221.68 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , =?utf-8?Q?Daniel_P=2E?= =?utf-8?Q?_Berrang=C3=A9?= , Richard Henderson , QEMU Developers , qemu-discuss , Christian Borntraeger , qemu-s390x , qemu-arm , qemu-ppc@nongnu.org, "open list:RISC-V" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Thomas Huth writes: > On 26/09/2019 15.46, Christian Borntraeger wrote: >> >> >> On 26.09.19 14:58, Daniel P. Berrang=C3=A9 wrote: >>> On Thu, Sep 26, 2019 at 08:50:36AM +0100, Peter Maydell wrote: >>>> On Thu, 26 Sep 2019 at 00:31, Alex Benn=C3=A9e 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 !=3D 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. > > Thomas -- Alex Benn=C3=A9e