The TCG emulation implements all the extensions described in the
RVA22U64 profile, both mandatory and optional. The mandatory extensions
will be enabled via the profile flag. We'll leave the optional
extensions to be enabled by hand.
Given that this is the first profile we're implementing in TCG we'll
need some ground work first:
- all profiles declared in riscv_profiles[] will be exposed to users.
TCG is the main accelerator we're considering when adding profile
support in QEMU, so for now it's safe to assume that all profiles in
riscv_profiles[] will be relevant to TCG;
- we'll not support user profile settings for vendor CPUs. The flags
will still be exposed but users won't be able to change them;
- profile support, albeit available for all non-vendor CPUs, will be
based on top of the new 'rv64i' CPU. Setting a profile to 'true' means
enable all mandatory extensions of this profile, setting it to 'false'
will disable all mandatory profile extensions of the CPU, which will
obliterate preset defaults. This is not a problem for a bare CPU like
rv64i but it can allow for silly scenarios when using other CPUs. E.g.
an user can do "-cpu rv64,rva22u64=false" and have a bunch of default
rv64 extensions disabled. The recommended way of using profiles is the
rv64i CPU, but users are free to experiment.
For now we'll handle multi-letter extensions only. MISA extensions need
additional steps that we'll take care later. At this point we can boot a
Linux buildroot using rva22u64 using the following options:
-cpu rv64i,rva22u64=true,sv39=true,g=true,c=true,s=true
Note that being an usermode/application profile we still need to
explicitly set 's=true' to enable Supervisor mode to boot Linux.
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20231218125334.37184-11-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
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