Date: Wed, 22 Aug 2001 01:27:49 -0700 From: Peter Wemm <peter@wemm.org> To: tlambert2@mindspring.com Cc: Mitsuru IWASAKI <iwasaki@jp.FreeBSD.org>, arch@FreeBSD.ORG, audit@FreeBSD.ORG, kumabu@t3.rim.or.jp Subject: Re: CFR: Timing to enable CR4.PGE bit Message-ID: <20010822082749.ED86038FD@overcee.netplex.com.au> In-Reply-To: <3B836737.9C15EA8@mindspring.com>
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Terry Lambert wrote: > Peter Wemm wrote: > > Terry Lambert wrote: > > > Mitsuru IWASAKI wrote: > > > > > This part is fine. > > > > > > > > OK, I'll commit this one first. > > > > > > What does setting PGE early do for you? > > > > The change is to avoid violating the rules in the CPU developers > > guide. Did you read the thread? > > Yes. I still don't get what rules are being broken (no one > quoted anything in comments inline in the code, citing the > relevent pages in the guide, with a URL for the guide, for > example). > > Let me ask again: what was broken before that is now fixed? The very first article in the thread said: ======== According to developer's manual from Intel site, ftp://download.intel.com/design/PentiumII/manuals/24319202.pdf ---- 2.5. CONTROL REGISTERS [snip] PGE (2-17) Page Global Enable (bit 7 of CR4). (Introduced in the P6 family processors.) Enables the global page feature when set; disables the global page feature when clear. [snip] In addition, the bit must not ^^^^^^^^^^^^^^^^ be enabled before paging is enabled via CR0.PG. Program correctness ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ may be affected by reversing this sequence, and processor performance will be impacted. ---- Currently, we enable CR4.PGE bit in create_pagetables, then enable CR0.PG in locore.s. This seems to violate Intel's note. ====== This was in: Message-id: <20010809035801V.iwasaki@jp.FreeBSD.org> Subject: CFR: Timing to enable CR4.PGE bit From: Mitsuru IWASAKI <iwasaki@jp.FreeBSD.org> Date: Thu, 09 Aug 2001 03:58:01 +0900 To: arch@FreeBSD.ORG Cc: audit@FreeBSD.ORG, kumabu@t3.rim.or.jp .. which is why I asked if you read the entire thread. I thought that quote was quite clear that we were in violation. Cheers, -Peter -- Peter Wemm - peter@FreeBSD.org; peter@yahoo-inc.com; peter@netplex.com.au "All of this is for nothing if we don't go to the stars" - JMS/B5 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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