[Qemu-arm] [PATCH v2 0/6] Runtime pagesize computation

[Peter Maydell]

This set of patches is a development based on the ones from Vijaya:
the general idea is similar but I have tried to improve the interface
for defining the page size a bit.  I've also tweaked patches 2 and 3
to address code review comments.

The basic idea here is that:
 * the target CPU implementation has to opt into variable page size
   by defining TARGET_PAGE_BITS_VARY, and then calling
   set_preferred_target_page_bits() in its realize function
   with whatever the CPU as instantiated actually requires
 * the machine also has to opt in, by specifying a new MachineClass
   field which states the value they guarantee will be no greater
   than the preferred page size for any CPU they create
 * we finalize the decision about page size in cpu_exec_init_all()
   (and then later attempts to create CPUs which can't cope with
   that decision are failed)

I would ideally have liked to finalize things much later, but
this is in practice hugely difficult because so many things
(in particular all the address space/memory system code)
assume the target page size is known.

Note that setting minimum_page-bits for a machine is a migration
compatibility break (the RAM migration format assumes both sides
have the same idea of a page size). Mismatches will probably
result in an unhelpfully obscure migration failure. (Possibly we
could have the migration send the page size if it was different
from TARGET_PAGE_BITS_MIN so we at least got a nice error?)

This could in theory be extended to the user-mode binaries,
but for the moment I have just required them to define a
fixed TARGET_PAGE_BITS.

NB: I have only very lightly tested these and haven't attempted
to measure performance at all. There is an assert() in the
definition of TARGET_PAGE_BITS which is good for making sure
it isn't used before it's valid but not so good for speed.

thanks
-- PMM


Peter Maydell (3):
  cpu: Support a target CPU having a variable page size
  target-arm: Make page size a runtime setting
  hw/arm/virt: Set minimum_page_bits to 12

Vijaya Kumar K (3):
  migration: Remove static allocation of xzblre cache buffer
  exec.c: Remove static allocation of sub_section of sub_page
  translate-all.c: Compute L1 page table properties at runtime

 exec.c                 | 47 ++++++++++++++++++++++++++++++++---
 hw/arm/virt.c          |  2 ++
 include/exec/cpu-all.h |  8 ++++++
 include/hw/boards.h    |  7 ++++++
 include/qemu-common.h  | 13 ++++++++++
 migration/ram.c        |  4 ++-
 target-arm/cpu.c       | 24 ++++++++++++++++++
 target-arm/cpu.h       |  9 ++++---
 translate-all.c        | 67 +++++++++++++++++++++++++++++++++-----------------
 vl.c                   | 10 ++++++++
 10 files changed, 160 insertions(+), 31 deletions(-)

-- 
1.9.1