[PATCH 0/3] target/arm: Make the counter frequency default 1GHz for new CPUs, machines

[Peter Maydell]

In previous versions of the Arm architecture, the frequency of the
generic timers as reported in CNTFRQ_EL0 could be any IMPDEF value,
and for QEMU we picked 62.5MHz, giving a timer tick period of 16ns.
In Armv8.6, the architecture standardized this frequency to 1GHz.

Because there is no ID register feature field that indicates whether a
CPU is v8.6 or that it ought to have this counter frequency, we
implement this by changing our default CNTFRQ value for all CPUs, with
exceptions for backwards compatibility:

 * CPU types which we already implement will retain the old
   default value. None of these are v8.6 CPUs, so this is
   architecturally OK.
 * CPUs used in versioned machine types with a version of 9.0
   or earlier will retain the old default value.

The upshot is that the only CPU type that changes is 'max'; but any
new type we add in future (whether v8.6 or not) will also get the new
1GHz default (assuming we spot in code review any attempts to set
the ARM_FEATURE_BACKCOMPAT_CNTFRQ flag on new CPU types as a result
of cut-n-paste from an older CPU initfn ;-)).

It remains the case that the machine model can override the default
value via the 'cntfrq' QOM property (regardless of the CPU type).

Patch 1 is Paolo's "add the new versioned machine types" patch that
he sent out last month; patch 2 is some preliminary cleanup so that
we set the default cntfrq value in exactly one place, and patch 3
is the mechanics to set the default appropriately for the two
back-compat scenarios.

thanks
-- PMM

Paolo Bonzini (1):
  hw: Add compat machines for 9.1

Peter Maydell (2):
  target/arm: Refactor default generic timer frequency handling
  target/arm: Default to 1GHz cntfrq for 'max' and new CPUs

 include/hw/boards.h        |  3 +++
 include/hw/i386/pc.h       |  3 +++
 target/arm/cpu.h           | 11 +++++++++
 target/arm/internals.h     | 15 +++++++++---
 hw/arm/virt.c              | 11 +++++++--
 hw/core/machine.c          |  5 ++++
 hw/i386/pc.c               |  3 +++
 hw/i386/pc_piix.c          | 17 +++++++++++---
 hw/i386/pc_q35.c           | 14 ++++++++++--
 hw/m68k/virt.c             | 11 +++++++--
 hw/ppc/spapr.c             | 17 +++++++++++---
 hw/s390x/s390-virtio-ccw.c | 14 +++++++++++-
 target/arm/cpu.c           | 47 ++++++++++++++++++++++++++------------
 target/arm/cpu64.c         |  2 ++
 target/arm/helper.c        | 16 ++++++-------
 target/arm/tcg/cpu32.c     |  4 ++++
 target/arm/tcg/cpu64.c     | 18 +++++++++++++++
 17 files changed, 173 insertions(+), 38 deletions(-)

-- 
2.34.1