Re: [PATCH for-9.0 v11 10/18] target/riscv/tcg: add user flag for profile support

[Andrew Jones]

On Thu, Nov 23, 2023 at 03:51:14PM -0300, Daniel Henrique Barboza wrote:
> 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>
> ---
>  target/riscv/tcg/tcg-cpu.c | 80 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 80 insertions(+)
>

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>