Messages in this thread | | | Date | 1 Feb 2014 16:17:10 -0500 | From | "George Spelvin" <> | Subject | Re: [PATCH] Make math_state_restore() save and restore the interrupt flag |
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> .. which *does* actually bring up something that might work, and might > be a good idea: remove the "restore math state or set TS" from the > normal kernel paths *entirely*, and move it to the "return to user > space" phase.
This definitely seems much more sensible. For processors without optimized context save/restore, the decision whether to restore eagerly is best made once the kernel has decided what it's returning *to*.
From an interrupt handler, there are now three cases: 1) FPU not in use, available for immediate use. 2) FPU in use by user-space; save to <location> before using. 3) FPU in use by kernel code; may not be used (unless we want to add nested FPU state save hair).
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