On 8/25/25 20:03, BALATON Zoltan wrote:
On Mon, 25 Aug 2025, Harsh Prateek Bora wrote:
On 8/25/25 17:52, Thomas Huth wrote:
On 25/08/2025 14.08, Harsh Prateek Bora wrote:
On 8/25/25 17:28, Thomas Huth wrote:
As I said, qemu-system-ppc64 is currently a full superset of
qemu-system- ppc. The ppc64 binary contains all the 32-bit code,
you can perfectly run a "g3beige" or "bamboo" machine with
qemu-system-ppc64, too. By disabling the ppe42 code in the ppc64
binary, this would now introduce an execption to that unwritten
rule, so I'd expect that we'd not rather want to do this now.
My understanding is that above holds true only for default builds which
builds all targets. We certainly do not build 32 bit ppc code when
using
--configure target-list=ppc64-softmmu. (we have ppc-softmmu for 32
bit though)
We do build 32-bit machines in ppc64-softmmu but leave out 64-bit from
ppc-softmmu so it's only one way.
Just give it a try:
./configure --target-list=ppc64-softmmu --disable-docs
make -j$(nproc)
./qemu-system-ppc64 -M g3beige
... works perfectly fine for me.
This would work because the respective code is not restricted with
#ifndef TARGET_PPC64.
However, there are instance like below in hw/ppc/mac_oldworld.c:
static void heathrow_class_init(ObjectClass *oc, const void *data)
{
MachineClass *mc = MACHINE_CLASS(oc);
FWPathProviderClass *fwc = FW_PATH_PROVIDER_CLASS(oc);
mc->desc = "Heathrow based PowerMac";
mc->init = ppc_heathrow_init;
mc->block_default_type = IF_IDE;
/* SMP is not supported currently */
mc->max_cpus = 1;
#ifndef TARGET_PPC64
mc->is_default = true;
#endif
This is only because the default machine for ppc64-softmmu is different
than for ppc-softmmu as the 64-bit machines don't exist in ppc-softmmu
but ppc64-softmmu had different default machine before machines from
qemu-system-ppc got included in qemu-system-ppc64 so it kept that.
(Looks like the default used to be mac_newworld before commit
159f8286b760dea but wasn't changed to match but to something else.) The
default machines are arbitrary, we could make "none" the default and
always require users to supply -machine but that would break existing
command lines so this wasn't done.
Similarly, we have multiple instances with #else block for #ifdef
TARGET_PPC64 which doesnt get compiled with ppc64-softmmu, but only with
ppc-softmmu meant for 32-bit targets. See target/ppc/excp_helper.c for
example.
This is again leaving out 64-bit code from ppc-softmmu but as Thomas
says 32-bit machines are always included in qemu-softmmu-ppc64. I can't
find the commit which changed this, previously we had these to be
separate and since some types are different in ppc64-softmmu it wasn't
clear if that could cause any problems for 32-bit CPUs and machines so
ppc-softmmu was kept until that's cleaned up which never happened. There
are also some pecularities in some machines like mac_newworld that
behaves differently in qemu-system-ppc and qemu-system-ppc64 and the
potentially lower performance of qemu-system-ppc64 in emulating 32-bit
machines which is why we still have ppc-softmmu.
Ok, I see. So, if we wish to keep the 32-bit machines supported with
qemu-system-ppc64, we will have them co-exist with run-time checks for
!ppc64 and/or "unlikely" operations in the hot path routines, which
wouldnt be needed otherwise. I hope we can deal with run-time checks for
!ppc64 if such ops increase.
Thanks to Thomas and you for clarifying this.
regards,
Harsh
Regards,
BALATON Zoltan
regards,
Harsh
AFAIK we don't have a switch to disable 32-bit code in the ppc64 binary.
Thomas
