From 8067e9c0b306312f870d4fe2cd32afe72e7400ff Mon Sep 17 00:00:00 2001 From: lkcl Date: Thu, 2 Sep 2021 12:59:37 +0100 Subject: [PATCH] --- openpower/sv/ldst.mdwn | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/openpower/sv/ldst.mdwn b/openpower/sv/ldst.mdwn index 9037dc04e..cc2161fc8 100644 --- a/openpower/sv/ldst.mdwn +++ b/openpower/sv/ldst.mdwn @@ -233,6 +233,14 @@ cache-inhibited LD should be performed, followed by a VSPLAT-augmented mv. ffirst LD/ST to multiple pages via a Vectorised base is considered a security risk due to the abuse of probing multiple pages in rapid succession and getting feedback on which pages would fail. Therefore in these special circumstances requesting ffirst with a vector base is instead interpreted as element-strided LD/ST. See +High security implementations where any kind of speculative probing +of memory pages is considered a risk should take advantage of the fact that +implementations may truncate VL at any point, without requiring software +to be rewritten and made non-portable. Such implementations may choose +to *always* set VL=1 which will have the effect of terminating any +speculative probing (and also adversely affect performance), but will +at least not require applications to be rewritten. + # LOAD/STORE Elwidths Loads and Stores are almost unique in that the OpenPOWER Scalar ISA @@ -261,7 +269,7 @@ is treated effectively as completely separate and distinct from SV augmentation. This is primarily down to quirks surrounding LE/BE and byte-reversal in OpenPOWER. -It is unfortubately possible to request an elwidth override on the memory side which +It is unfortunately possible to request an elwidth override on the memory side which does not mesh with the operation width: these result in `UNDEFINED` behaviour. The reason is that the effect of attempting a 64-bit `sv.ld` operation with a source elwidth override of 8/16/32 would result in @@ -315,7 +323,6 @@ and other modes have all been removed, for clarity and simplicity: if (bytereverse): memread = byteswap(memread, op_width) - # check saturation. if svpctx.saturation_mode: ... saturation adjustment... -- 2.30.2