[PATCH v2 0/6] riscv: zicntr/zihpm flags and disable support

[Daniel Henrique Barboza]

Hi,

This is a follow-up of the work done in [1] after review comments made
in the rva22u64 profile support review [2].

zicntr and zihpm are already implemented by QEMU before they were added
as discrete extensions by RVI. This puts QEMU in a weird spot because it
has enabled default extensions that aren't togglable on/off via user
flags and aren't reported in riscv,isa as present.

There's no reason to no treat both zicntr and zihpm as regular
extensions, reporting their existence in riscv,isa DT and allowing users
to disable them. This will also benefit us in the incoming profile
support, since disabling a profile should disable all its mandatory
extensions, and for the rva22u64 profile this means that both zicntr and
zihpm should be disabled as well. 

Let's add user flags and disable support for both in all accelerators
(TCG and KVM). FWIW Linux boot doesn't seem to care about the lack of
both zicntr and zihpm when running TCG, although attempting to use the
timers will result in SIGILL.


[1] 
https://lore.kernel.org/qemu-riscv/20230717215419.124258-1-dbarboza@ventanamicro.com/
[2] 
https://lore.kernel.org/qemu-riscv/20231017-e7a4712137165b59844499e3@orel/T/#m3bb0e3c9b00d9edd168da9f7de0bc26df4f7d6ab

Daniel Henrique Barboza (6):
  target/riscv/cpu.c: add zicntr extension flag
  target/riscv/tcg: add ext_zicntr disable support
  target/riscv/kvm: add zicntr reg
  target/riscv/cpu.c: add zihpm extension flag
  target/riscv/tcg: add ext_zihpm disable support
  target/riscv/kvm: add zihpm reg

 target/riscv/cpu.c         | 15 +++++++++++++++
 target/riscv/cpu_cfg.h     |  2 ++
 target/riscv/csr.c         |  4 ++++
 target/riscv/kvm/kvm-cpu.c |  2 ++
 target/riscv/tcg/tcg-cpu.c | 21 +++++++++++++++++++++
 5 files changed, 44 insertions(+)

-- 
2.41.0