[PATCH 0/5] target/arm: Support variable sized coprocessor registers

[Gavin Shan]

There are two arrays for each CPU, to store the indexes and values of the
coprocessor registers. Currently, 8 bytes fixed storage space is reserved
for each coprocessor register. However, larger coprocessor registers have
been defined and exposed by KVM. Except SVE registers, no coprocessor
register exceeds 8 bytes in size. It doesn't mean large coprocessor registers
won't be exploited in future. For example, I'm looking into SDEI virtualization
support, which isn't merged into Linux upstream yet. I have plan to add
several coprocessor ("firmware pseudo") registers to assist the migration.

This series adds one more array, to track the position or location in the
storage array (@cpreg_values) for the corresponding coprocessor register.
The storage space for one particular coprocessor register is always to
8 bytes so that we needn't worry about the alignment issue. In this way,
the coprocessor register size can be variable.

I had some internal discussion with Eric and Drew. They suggested to
send one mail to qemu-arm@nongnu.org, asking if there is any challenges
to support variable sized coprocessor registers. So another intention
of this series is to invoke the discussion.

PATCH[1-3] adds one more array (@cpreg_value_indexes) to track the location
in the storage array (@cpreg_values) for coprocessor registers. The storage
space for one particular coprocessor register is determined by the additional
array, which is named as indirect addressing mode. Each coprocessor register
is still having 8 bytes fixed storage space, so that thd old mechanism
(direct addressing mode) and indirect address mode can co-exist, event in
migration circumstance. PATCH[4] migrates the additional array. PATCH[5]
initializes @cpreg_value_indexes for KVM.

Gavin Shan (5):
  target/arm/tcg: Indirect addressing for coprocessor register storage
  target/arm/hvf: Indirect addressing for coprocessor register storage
  target/arm/kvm: Indirect addressing for coprocessor register storage
  target/arm: Migrate coprocessor register indirect addressing
    information
  target/arm/kvm: Support coprocessor register with variable size

 target/arm/cpu.h     | 12 +++++--
 target/arm/helper.c  | 27 +++++++++-----
 target/arm/hvf/hvf.c | 20 +++++++++--
 target/arm/kvm.c     | 85 ++++++++++++++++++++++++++++++++++++++------
 target/arm/machine.c | 30 ++++++++++++----
 5 files changed, 145 insertions(+), 29 deletions(-)

-- 
2.23.0