On 18.07.2022 12:11, Andrew Cooper wrote: > On 18/07/2022 11:00, Jan Beulich wrote: >> On 18.07.2022 09:18, Andrew Cooper wrote: >>> @@ -199,9 +211,18 @@ void check_wakeup_from_wait(void) >>> } >>> >>> /* >>> - * Hand-rolled longjmp(). Returns to __prepare_to_wait(), and lands >>> on a >>> - * `rep movs` instruction. All other GPRs are restored from the >>> stack, so >>> - * are available for use here. >>> + * Hand-rolled longjmp(). >>> + * >>> + * check_wakeup_from_wait() is always called with a shallow stack, >>> + * immediately after the vCPU has been rescheduled. >>> + * >>> + * Adjust %rsp to be the correct depth for the (deeper) stack we want >>> to >>> + * restore, then prepare %rsi, %rdi and %rcx such that when we >>> intercept >>> + * the rep movs in __prepare_to_wait(), it copies from wqv->stack over >>> the >>> + * active stack. >> I'm struggling with the use of "intercept" here, but I guess that's just >> because I'm not a native speaker. > > "intercept" is the same terminology used in the middle of > __prepare_to_wait()'s block. > > It's because we have a weird setup where this is (now) a noreturn > function merging into the middle of a function which already executed once. > > I'm happy to change it if it's unclear, but I can't think of a better > description.
"... when we go back to ..."? (But I'm not meaning to insist on a wording change.) Jan
