Hi,
As discussed in v6, all our problems with the profile implementation
cames from the rv64 CPU and how to deal with its defaults. Enabling a
profile on top of it is straightforward, but disabling it (either via a
script trying to undo a profile enablement, or users doing something
silly) makes things complicated - disabling all the mandatory extensions
will overwrite the CPU defaults, but doing nothing is weird considering
how QEMU options work. And therein lies the rub: we didn't have any
other way of consuming profiles, so we were stuck dancing around rv64
defaults and what to do with them.
In this v7 we're adding a new CPU called 'rv64i'. This is a new type of
CPUs, called 'bare', that doesn't inherit any defaults and allows users
to enable/disable extensions at will. This CPU is implementing bare
RV64I for a reason: this is the mandatory ISA for profiles support.
All the design around profile support is now made on top of how rv64i
works. Other non-vendor CPUs (like rv64) can still use profiles, but
now we're not concerned about what happens if an user does '-cpu
rv64,rva22u64=false'. In short, we recommend using profiles with rv64i
but we won't forbid using it with rv64 (in particular because stock rv64
does not implement rva22u64, which is surprising giving it has a lot of
defaults ...). Patches 1, 2 and 3 implements rv64i.
Another noticeable change was made in patches 15 and 16. We're now
exposing the profile flag to all CPUs. In the end a profile is just a
set of mandatory extensions and conditions that must be met. If the
conditions are met we should enable the flag, regardless of user input.
This is done by changes in patch 15. Patch 16 changes
query-cpu-model-expansion to show profile flags.
Patches based on top of Alistair's riscv-to-apply.next.
Patches missing acks: 1, 2, 3, 5, 15, 16
Changes from v6:
- patch 1 (new):
- create vendor CPU type
- patch 2 (new):
- check for 'if vendorCPU' instead of 'if !genericCPU'
- patch 3 (new):
- add rv64i CPU
- patch 5 (former patch 2 from v6):
- drop the CB_DEF_VALUE define
- patch 6 (fomer patch 3 from v6):
- mention cbop block size in commit msg
- patch 9 (former patch 6 from v6):
- removed the "no-op" when disabling a profile
- rewrote the commit msg to reflect that the design is made on top of the
rv64i CPU
- patch 12 (fomer patch 9 from v6):
- do not disable RVI when disabling a profile
- patch 15 (patch 12 from v6):
- previous acks revoked due to the amount of changes made
- disable profile flags if there are missing mandatory extensions during
finalize()
- enable profile flags if all its preconditions are met during
finalize()
- patch 16 (new):
- add profile flags to query-cpu-model-expansion
- v6 link:
https://lore.kernel.org/qemu-riscv/20231028085427.707060-1-dbarb...@ventanamicro.com/
Daniel Henrique Barboza (16):
target/riscv: create TYPE_RISCV_VENDOR_CPU
target/riscv/tcg: do not use "!generic" CPU checks
target/riscv: add rv64i CPU
target/riscv: add zicbop extension flag
target/riscv/tcg: add 'zic64b' support
riscv-qmp-cmds.c: expose named features in cpu_model_expansion
target/riscv: add rva22u64 profile definition
target/riscv/kvm: add 'rva22u64' flag as unavailable
target/riscv/tcg: add user flag for profile support
target/riscv/tcg: add MISA user options hash
target/riscv/tcg: add riscv_cpu_write_misa_bit()
target/riscv/tcg: handle profile MISA bits
target/riscv/tcg: add hash table insert helpers
target/riscv/tcg: honor user choice for G MISA bits
target/riscv/tcg: validate profiles during finalize
riscv-qmp-cmds.c: add profile flags in cpu-model-expansion
hw/riscv/virt.c | 5 +
target/riscv/cpu-qom.h | 3 +
target/riscv/cpu.c | 96 ++++++++++-
target/riscv/cpu.h | 13 ++
target/riscv/cpu_cfg.h | 3 +
target/riscv/kvm/kvm-cpu.c | 7 +-
target/riscv/riscv-qmp-cmds.c | 44 ++++-
target/riscv/tcg/tcg-cpu.c | 301 +++++++++++++++++++++++++++++-----
8 files changed, 412 insertions(+), 60 deletions(-)
--
2.41.0
