On Wed, Mar 27, 2024 at 05:54:56PM +0100, Philippe Mathieu-Daudé wrote: > Per Daniel suggestion [*]: > > > isapc could arguably be restricted to just 32-bit CPU models, > > because we should not need it to support any feature that didn't > > exist prior to circa 1995. eg refuse to start with isapc, if 'lm' > > is present in the CPU model for example. > > Display a warning when such CPU is used: > > $ qemu-system-x86_64 -monitor stdio -S -M isapc -cpu Westmere > qemu-system-x86_64: warning: Use of 64-bit CPU 'Westmere' is deprecated on > the ISA-only PC machine > QEMU 8.2.91 monitor - type 'help' for more information > (qemu) q > > $ qemu-system-x86_64 -monitor stdio -S -M isapc -cpu athlon > QEMU 8.2.91 monitor - type 'help' for more information > (qemu) q
I've thought of a possible problem here.. $ qemu-system-x86_64 -monitor stdio -S -M isapc -cpu max is going to enable 'lm' (and a bazillion other new features) for 'isapc', which is a shame, as 'max' is something we want to be usable in general. I'm not sure how to square that circle. I might suggest that 'isapc' instead only makes sense in the context of qemu-system-i386, since that only has 32-bit CPUs. We wanted to kill that binary in favour of qemu-system-x86_64 for both 32 & 64 bit though, so we can't block 'isapc' from qemu-system-x86_64. > > [*] https://lore.kernel.org/qemu-devel/zgqks4rpmst5x...@redhat.com/ > > Suggested-by: Daniel P. Berrangé <berra...@redhat.com> > Signed-off-by: Philippe Mathieu-Daudé <phi...@linaro.org> > --- > docs/about/deprecated.rst | 7 +++++++ > include/hw/i386/pc.h | 1 + > hw/i386/pc_piix.c | 14 ++++++++++++++ > 3 files changed, 22 insertions(+) > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > index 7b548519b5..345c35507f 100644 > --- a/docs/about/deprecated.rst > +++ b/docs/about/deprecated.rst > @@ -208,6 +208,13 @@ is no longer packaged in any distro making it harder to > run the > ``check-tcg`` tests. Unless we can improve the testing situation there > is a chance the code will bitrot without anyone noticing. > > +64-bit (x86_64) CPUs on the ``isapc`` machine (since 9.0) > +''''''''''''''''''''''''''''''''''''''''''''''''''''''''' > + > +The ``isapc`` machine aims to emulate old PC machine without PCI was > +generalized, so hardware available around 1995, before 64-bit intel > +CPUs were produced. > + > System emulator machines > ------------------------ > > diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h > index 27a68071d7..2d202b9549 100644 > --- a/include/hw/i386/pc.h > +++ b/include/hw/i386/pc.h > @@ -96,6 +96,7 @@ struct PCMachineClass { > const char *default_south_bridge; > > /* Compat options: */ > + bool deprecate_64bit_cpu; /* Specific to the 'isapc' machine */ > > /* Default CPU model version. See x86_cpu_set_default_version(). */ > int default_cpu_version; > diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c > index 18ba076609..2e5b2efc33 100644 > --- a/hw/i386/pc_piix.c > +++ b/hw/i386/pc_piix.c > @@ -182,7 +182,20 @@ static void pc_init1(MachineState *machine, const char > *pci_type) > } > > pc_machine_init_sgx_epc(pcms); > + > x86_cpus_init(x86ms, pcmc->default_cpu_version); > + if (pcmc->deprecate_64bit_cpu) { > + X86CPU *cpu = X86_CPU(first_cpu); > + > + if (cpu->env.features[FEAT_8000_0001_EDX] & CPUID_EXT2_LM) { > + const char *cpu_type = object_get_typename(OBJECT(first_cpu)); > + int cpu_len = strlen(cpu_type) - strlen(X86_CPU_TYPE_SUFFIX); > + > + warn_report("Use of 64-bit CPU '%.*s' is deprecated" > + " on the ISA-only PC machine", > + cpu_len, cpu_type); > + } > + } > > if (kvm_enabled()) { > kvmclock_create(pcmc->kvmclock_create_always); > @@ -918,6 +931,7 @@ static void isapc_machine_options(MachineClass *m) > pcmc->gigabyte_align = false; > pcmc->smbios_legacy_mode = true; > pcmc->has_reserved_memory = false; > + pcmc->deprecate_64bit_cpu = true; > m->default_nic = "ne2k_isa"; > m->default_cpu_type = X86_CPU_TYPE_NAME("486"); > m->no_parallel = !module_object_class_by_name(TYPE_ISA_PARALLEL); > -- > 2.41.0 > With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
