[ORLinux] l.mac* instructions
jonas at southpole.se
Sun Jul 3 08:43:30 CEST 2011
The patch looks good. Thanks.
Noting that you put the register save/restore into the exception
handling hot path, I began to dig into the arch spec for this
instruction and a couple of questions came up:
i) The spec refers to "synchronize-mac"... how is this handled across
ii) Does the MAC pipeline need to be "synchronized" before
saving/restoring its state in an exception handler?
iii) Is l.macrc the only way to "synchronize"? We lose the high word
when we do so...
iv) Is a sequence of MAC instructions even interruptible?
The spec doesn't really seem to make this clear. Hopefully, somebody
else can shine some light on this.
On Fri, 2011-07-01 at 22:47 +0000, King, Samuel Talmadge wrote:
> Hi Jonas,
> I am still getting used to git and I made a mistake -- the version I sent below was wrong. Here is an updated version that is correct, has a more meaningful comment, mentions the three instructions explicitly in the Kconfig help item, and excludes all of the whitespace changes:
> From 66ff477fb545cf088c3b70e2e2d775659b5951e5 Mon Sep 17 00:00:00 2001
> From: Sam King <kingst at illinois.edu>
> Date: Fri, 1 Jul 2011 17:27:45 -0500
> Subject: [PATCH 2/2] Added support for storing the MAC as part of a thread's context.
> Added machi and maclo to pt_regs and added code for saving and
> restoring these values on the exception paths. Added configuration
> for specifying when these instructions are supported by an
> Signed-off-by: Sam King <kingst at illinois.edu>
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