[PATCH 0/2] i386: use better matching family/model/stepping for generic CPUs

[Daniel P . Berrangé]

This is in response to this bug report:

   https://gitlab.com/qemu-project/qemu/-/issues/191

The generic 'qemu64' and 'max' CPUs currently defined to report a
family/model/stepping that approximately corresponds to an AMD K7
vintage architecture. The K7 series predates the introduction of
64-bit support by AMD in the K8 series. This has been reported to
lead to LLVM complaints about generating 64-bit code for a 32-bit
CPU target

  LLVM ERROR: 64-bit code requested on a subtarget that doesn't support it!

The bug report is fairly limited, but it suggests LLVM looks at the
family/model/stepping and decides it to be 32-bit, despite qemu64
reporting it is 64-bit capable. I've not reproduced this myself,
however, so I'm largely trusting the original reporter's diagnosis

Of course interpreting the family/model/stepping only makes sense
with scoped to the reported vendor ID.  Under TCG, the vendor is
honoured, but AFAICT, under KVM the vendor defined by the QEMU
model model is ignored and the real host vendor passed through.
This will make the chosen family/model/stepping non-sensical when
run under KVM on an Intel host.

None the less these patches change to report a CPUID with the
family, model and stepping taken from a

 AMD Athlon(tm) 64 X2 Dual Core Processor 4000+

which is one of the first 64-bit AMD CPUs. This is at least more
accurate in terms of the static CPU model definition, even if it
is still nonsense in the case where KVM overrides the vendor to
be non-AMD.

Daniel P. Berrangé (2):
  i386: use better matching family/model/stepping for 'qemu64' CPU
  i386: use better matching family/model/stepping for 'max' CPU

 hw/i386/pc.c      |  6 +++++-
 target/i386/cpu.c | 12 +++++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)

-- 
2.31.1