On 27/03/2024 16:54, 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
[*] https://lore.kernel.org/qemu-devel/ZgQkS4RPmSt5Xa08@xxxxxxxxxx/
Suggested-by: Daniel P. Berrangé <berrange@xxxxxxxxxx>
Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
---
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);
The logic around checking CPUID_EXT2_LM looks good to me. Slightly curious as to
whether people feel updating PCMachineClass is necessary, or you can simply do
qdev_get_machine() and use object_dynamic_cast() to see if the machine matches
MACHINE_NAME("isapc") and warn that way?
FWIW I'd be amazed if anyone were actually overriding the default and trying to do
this, but I guess that's what the warn_report() is for.... anyhow:
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@xxxxxxxxxxxx>
ATB,
Mark.
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