[PATCH v2] riscv: Add tracepoints for SBI calls and returns

[Conor Dooley]

On Thu, Mar 21, 2024 at 04:01:25PM -0700, Samuel Holland wrote:
> These are useful for measuring the latency of SBI calls. The SBI HSM
> extension is excluded because those functions are called from contexts
> such as cpuidle where instrumentation is not allowed.
> 
> Reviewed-by: Andrew Jones <ajones at ventanamicro.com>
> Signed-off-by: Samuel Holland <samuel.holland at sifive.com>

I seem to have bisected a boot failure on v6.11-rc# to this commit,
with a crash before the kernel ever gets to output anything - even on
the bootconsole. For one of these crashes I got the below (which is
actually U-Boots exception handler), but most of the time - nothing at
all. I'll try to decodecode that tomorrow and fish out a config, because
this is either config or toolchain dependant (I saw it in work, with a
slightly different config etc to what I have here).


Starting kernel ...
 
Unhandled exception: Load access fault
EPC: 000000008020e09c RA: 000000008020e510 TVAL: ffffffff81cbf1f0
EPC: 00000000408a009c RA: 00000000408a0510 reloc adjusted
 
Code: 3597 01a4 b583 1f45 5613 0035 9a61 95b2 (618c)
 
 
resetting ...
reset not supported yet
### ERROR ### Please RESET the board ###


Cheers,
Conor.
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