On 9/26/19 12:50 AM, 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.
Agreed. I think this discussion should be more about TCG. >> @@ -745,19 +744,22 @@ case "$cpu" in >> ;; >> armv*b|armv*l|arm) >> cpu="arm" >> - supported_cpu="yes" >> ;; > > I'll leave others to voice opinions about their architectures, > but I still have 32-bit arm in my test set for builds, and > I'm pretty sure we have users (raspi users, for a start). I'd really like to know what raspi users might be using qemu for. Depending on that answer, perhaps it would be sufficient for arm32 tcg to only support 32-bit guests. For context, the discussion that Alex and I were having was about int128_t, and how to support that directly in tcg (especially to/from helpers), and how that might be vastly easier if we didn't have to consider 32-bit hosts. r~
