Require OS to start in HS-mode #27
Conversation
BRS combines operating system and hypervisor in its definition for 'OS' which makes it a more convenient term to use in requirements. Signed-off-by: Andrew Jones <[email protected]>
The H extension is required by RVA23 which is required by the server platform. Ensure that when the OS/hypervisor is started that it's available. Resolves: #11 Signed-off-by: Andrew Jones <[email protected]>
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Totally makes sense. |
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Thinking more about this, "starting the OS" is a bit too vague in UEFI land. Do you mean the OS loader (an UEFI application) must start in HS mode? Or did you mean at actual hand-off from UEFI (e.g. at ExitBootServices time) that the execution continues in HS mode? Consider if we didn't have a #30 rule, and an Sv57 system actually placed RAM at bit 56. Then BRS UEFI_030 rule could never be met, right? But if the UEFI implementation partially ran in HS mode it could get away with using the G-stage tables to provide a 1:1 mapping and allow protecting regions - riscv-non-isa/riscv-brs#221. I'm not saying we should or should not allow such a situation, but the vague wording here could enable technically starting the OS in HS mode, yet the OS boot loader runs in VS mode. So let's use concise language. (I would, for the sake of simplicity, require the actual UEFI implementation to run in HS mode, hand off to OS loader in HS mode, and leave the hart in HS mode after ExitBootServices) |
resolves issue #11