Re: [PATCH 00/10] Enable QEMU to run on browsers

[Kohei Tokunaga <ktokunaga.mail@gmail.com>]

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Hi Paolo,

> > > The biggest problem I'm seeing is we no longer support 64-bit guests
on
> > > 32-bit hosts, and don't plan to revert that.
> >
> > Yes, so the sixth patch ("[PATCH 06/10] include/exec: Allow using 64bit
> > guest addresses on emscripten") should be considered as a temporary
> > workaround, enabled only for Emsripten builds. It will be removed once
> > wasm64 gains broader support and is adopted in the Wasm backend.
>
> Maybe there's a way though. Currently we don't support 64-bit guests on
> 32-bit hosts, but more precisely we don't support 64-bit guests with
> 32-bit host word size.
>
>
> The wasm TCG backend is able to compile with 64-bit words:
>
> +#define TCG_TARGET_HAS_div_i64          1
> +#define TCG_TARGET_HAS_rem_i64          1
> etc.
>
> and if x32 was a thing it would as well.  In fact the changes in patch
> 6/10 are not a full revert, and the "#ifdef EMSCRIPTEN" could be changed
to
>
> #if HOST_LONG_BITS >= TARGET_LONG_BITS
> ... use uintptr_t
> #else
> ... use uint64_t
> #endif

Thank you for the feedback.

Yes, the Wasm backend can be compiled with 64-bit words. The change
regarding the macro looks good to me.

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