On 4/27/23 10:13, Thomas Huth wrote:
On 26/04/2023 12.59, Paolo Bonzini wrote:
On 4/25/23 15:38, Thomas Huth wrote:
- CPU types have different suffixes between the -x86_64 and -i386
variant (see TYPE_X86_CPU in cpu-qom.h) ... do we need to care
about this in the new qemu-system-i386 symlink run mode?
- The code in target/i386/tcg/sysemu/smm_helper.c looks like it
maybe needs a runtime switch, too ... or is it ok to leave this
hard-coded to the x86_64 version?
Yes, it would have to switch based on the CPU's LM feature.
Ok. BTW, what happens if you run qemu-system-x86_64 with -cpu lm=off
today? Isn't that a problem already?
Nothing special---I was thinking of migration compatibility from old
savefiles created with qemu-system-i386, but using LM would break
compatibility from old savefiles created with qemu-system-x86_64 and
32-bit CPU models.
A better way to go would be to have a separate property than LM (e.g.
64bit-smm-format=on|off), and add a "-global" based on -i386 vs. -x86_64.
Anyway, I'd like to get some feedback on this idea here... What
do you think of the idea of getting rid of the qemu-system-i386
binary this way in the future?
I wonder if we should take this a step further and rename
qemu-system-x86_64 to qemu-system-x86! Distros can if they wish
create symlinks to both qemu-system-i386 and qemu-system-x86_64.
Then we would name the CPUs "foo-x86" and alias them to foo-x86_64
and, if they don't have LM set, to foo-i386 as well.
I like the idea! ... we could maybe even go a step further and change
the default machine to "q35" in the -x86 binary (or use no default
machine at all), and switch back to "pc" as default if running in
-x86_64 or -i386 mode...
That's a clever way to move away from the "-M pc" default, indeed.
(BTW, on the user-mode emulation side qemu-i386 and qemu-x86_64 identify
the ABI, so the binaries cannot be unified. Still, it would be
beneficial to make qemu-i386 use the x86_64 emulation code, because
right now QEMU user-mode emulation---unlike real hardware---cannot run
32-bit binaries with new CPU models. So the above unification effort
would benefit both system and user-mode emulators).
Paolo
