From 5bc28c957934d0db1814f70779ccf0d5ab7bd70b Mon Sep 17 00:00:00 2001 From: lkcl Date: Sat, 25 Mar 2023 20:14:21 +0000 Subject: [PATCH] --- openpower/sv/rfc/ls008.mdwn | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/openpower/sv/rfc/ls008.mdwn b/openpower/sv/rfc/ls008.mdwn index 408578598..3fda6ee30 100644 --- a/openpower/sv/rfc/ls008.mdwn +++ b/openpower/sv/rfc/ls008.mdwn @@ -237,11 +237,20 @@ SVSTATE contains (and permits setting of): REMAPed: RA, RB, RC, RT and EA are the canonical (typical) register names associated with each bit, with RA being the LSB and EA being the MSB. See table below for ordering. When `SVme` is zero (0b00000) REMAP - is **fully disabled and inactive**. + is **fully disabled and inactive** regardless of the contents of + `SVSTATE`, `mi0-mi2/mo0-mo1`, or the four `SVSHAPEn` SPRs * mi0-mi2/mo0-mo1 - when the corresponding SVme bit is enabled, these indicate the SVSHAPE (0-3) that the corresponding register (RA etc) should use, as long as the register's corresponding SVme bit is set +Programmer's Note: the fact that REMAP is entirely dormant when `SVme` is zero +allows establishment of REMAP context well in advance, followed by utilising `svremap` +at a precise (or the very last) moment. Some implementations may exploit this +to cache (or take some time to prepare caches) in the background whilst other +(unrelated) instructions are being executed. This is particularly important to +bear in mind when using `svindex` which will require hardware to perform (and +cache) additional GPR reads. + Programmer's Note: when REMAP is activated it becomes necessary on any context-switch (Interrupt or Function call) to detect (or know in advance) that REMAP is enabled and to additionally save/restore the four SVSHAPE -- 2.30.2