tree 6b8741e7918022f13501e9309db5fa91837add5d
parent fea445e8fe9acea4f775a832815ee22bdf2b0222
author Daniel Henrique Barboza <dbarboza@ventanamicro.com> 1710275534 -0300
committer Alistair Francis <alistair.francis@wdc.com> 1711084245 +1000

target/riscv: do not enable all named features by default

Commit 3b8022269c added the capability of named features/profile
extensions to be added in riscv,isa. To do that we had to assign priv
versions for each one of them in isa_edata_arr[]. But this resulted in a
side-effect: vendor CPUs that aren't running priv_version_latest started
to experience warnings for these profile extensions [1]:

  | $ qemu-system-riscv32  -M sifive_e
  | qemu-system-riscv32: warning: disabling zic64b extension for hart
0x00000000 because privilege spec version does not match
  | qemu-system-riscv32: warning: disabling ziccamoa extension for
hart 0x00000000 because privilege spec version does not match

This is benign as far as the CPU behavior is concerned since disabling
both extensions is a no-op (aside from riscv,isa). But the warnings are
unpleasant to deal with, especially because we're sending user warnings
for extensions that users can't enable/disable.

Instead of enabling all named features all the time, separate them by
priv version. During finalize() time, after we decided which
priv_version the CPU is running, enable/disable all the named extensions
based on the priv spec chosen. This will be enough for a bug fix, but as
a future work we should look into how we can name these extensions in a
way that we don't need an explicit ext_name => priv_ver as we're doing
here.

The named extensions being added in isa_edata_arr[] that will be
enabled/disabled based solely on priv version can be removed from
riscv_cpu_named_features[]. 'zic64b' is an extension that can be
disabled based on block sizes so it'll retain its own flag and entry.

[1] https://lists.gnu.org/archive/html/qemu-devel/2024-03/msg02592.html

Reported-by: Clément Chigot <chigot@adacore.com>
Fixes: 3b8022269c ("target/riscv: add riscv,isa to named features")
Suggested-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Tested-by: Clément Chigot <chigot@adacore.com>
Message-ID: <20240312203214.350980-1-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>