Alistair Francis <alistai...@gmail.com> writes:
> On Thu, Sep 26, 2019 at 8:41 AM Alex Bennée <alex.ben...@linaro.org> wrote: >> >> >> Thomas Huth <th...@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.ben...@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
