target/riscv: add profile->present flag

target/riscv: add profile->present flag

Björn reported in [1] a case where a rv64 CPU is going through the
profile code path to enable satp mode. In this case,the amount of
extensions on top of the rv64 CPU made it compliant with the RVA22S64
profile during the validation of CPU 0. When the subsequent CPUs were
initialized the static profile object has the 'enable' flag set,
enabling the profile code path for those CPUs.

This happens because we are initializing and realizing each CPU before
going to the next, i.e. init and realize CPU0, then init and realize
CPU1 and so on. If we change any persistent state during the validation
of CPU N it will interfere with the init/realization of CPU N+1.

We're using the 'enabled' profile flag to do two distinct things: inform
cpu_init() that we want profile extensions to be enabled, and telling
QMP that a profile is currently enabled in the CPU. We want to be
flexible enough to recognize profile support for all CPUs that has the
extension prerequisites, but we do not want to force the profile code
path if a profile wasn't set too.

Add a new 'present' flag for profiles that will coexist with the 'enabled'
flag. Enabling a profile means "we want to switch on all its mandatory
extensions". A profile is 'present' if we asserted during validation
that the CPU has the needed prerequisites.

This means that the case reported by Björn now results in
RVA22S64.enabled=false and RVA22S64.present=true. QMP will recognize it
as a RVA22 compliant CPU and we won't force the CPU into the profile
path.

[1] https://lore.kernel.org/qemu-riscv/87y0usiz22.fsf@all.your.base.are.belong.to.us/

Reported-by: Björn Töpel <bjorn@kernel.org>
Fixes: 2af005d610 ("target/riscv/tcg: validate profiles during finalize")
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Message-ID: <20250528184407.1451983-4-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>