[Premier P550] OpenSBI does not delegate page faults

[CharlyCst]

While measuring the number of exits to OpenSBI on the Premier P550 we found out the page faults are not delegated to S-mode.

This incurs a huge performance penalty for us (as we virtualize OpenSBI) which is why we started investigating, but it also slows down standard deployments especially workloads that induces frequent page faults.

It seems this is caused by the missing default feature SBI_PLATFORM_DEFAULT_FEATURES here:

https://github.com/sifive/meta-sifive/blob/b954d91f654a53068d1c846dffd800bfe6bd37d0/recipes-bsp/opensbi/opensbi-sifive-hf-prem/0001-platform-Add-ESWIN-EIC770x-platform.patch#L373

Which in turns makes sbi_platform_has_mfaults_delegation evaluate to false and thus OpenSBI to not delegate page faults.

The Premier P550 can delegate page faults, so that seems like simple oversight.

Summary

• Observed behavior: OpenSBI does not delegate page fault, induces unnecessary overhead
• Expected behavior: OpenSBI should delegate page fault
• Branch: rel/meta-sifive/hifive-premier-p550
• Fix:
  Replace https://github.com/sifive/meta-sifive/blob/b954d91f654a53068d1c846dffd800bfe6bd37d0/recipes-bsp/opensbi/opensbi-sifive-hf-prem/0001-platform-Add-ESWIN-EIC770x-platform.patch#L373
  With:

  +	.features		= SBI_PLATFORM_DEFAULT_FEATURES,

[ganboing]

Charly (@CharlyCst) Just came across your post. I'm a P550 and advance RISCV user like you. Recently I'm sending patches to OpenSBI upstream to get this SoC supported out-of-box: https://lore.kernel.org/all/20251120093440.4533-1-ganboing@gmail.com/ You may also find my UART boot guide useful: https://github.com/ganboing/EIC770x-Docs/blob/main/board/bootchain/UART-Boot.md

The vendor OpenSBI upstreaming effort took so long, and I'm not sure if it's even started yet, so I decided to do it myself.