On 3/15/24 16:11, Bibo Mao wrote:
[snip] +KVM hypercall ABI +================= + +Hypercall ABI on KVM is simple, only one scratch register a0 and at most +five generic registers used as input parameter. FP register and vector register +is not used for input register and should not be modified during hypercall. +Hypercall function can be inlined since there is only one scratch register.
Maybe it's better to describe the list of preserved registers with an expression such as "all non-GPR registers shall remain unmodified after returning from the hypercall", to guard ourselves against future ISA state additions.
But I still maintain that it's better to promise less here, and only hint on the extensive preservation of context as an implementation detail. It is for not losing our ability to save/restore less in the future, should we decide to do so.
-- WANG "xen0n" Xuerui Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/
