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--- e820irc:irc_logs_for_e820_issue [2006/06/14 22:47]
ashieh created
+++ e820irc:irc_logs_for_e820_issue [2006/06/14 22:50] (current)
ashieh
@@ Line 77: / Line 77: @@
 </file>
-I fixed the 640KB reporting, but there were other problems:
+After an adventure through 16-bit real mode code. I fixed the 640KB e820 hole, but there were other problems with the E820 map:
+<file>
+Date: Mon, 12 Jun 2006 04:20:08 -0400
+From: "Alan Shieh" <alancshieh@gmail.com>
+To: Etherboot <Etherboot-discuss@lists.sourceforge.net>
+Subject: E820 map
+MIME-Version: 1.0
+Content-Type: text/plain; charset=ISO-8859-1; format=flowed
+Content-Transfer-Encoding: 7bit
+Content-Disposition: inline
+Delivered-To: alancshieh@gmail.com
+As discussed on IRC, my PXE booted Linux was not getting a E820 map
+that reflected the resident PXE stack.
+I tracked down the problem for my Etherboot 5.2 snapshot. _hide_memory
+only had 2 entries, one for the .text segment, and one for the heap.
+However, the UNDI Code and Data segments are allocated from base
+memory, which is not covered by either of these regions.
+So I fixed hide_etherboot() and _hide_memory to reflect the UNDI
+segments, and now they are correctly omitted from the e820 map.
+However, I'm still wary of my e820 map:
+ BIOS-e820: 0000000000000000 - 000000000009e000 (usable)
+ BIOS-e820: 0000000000100000 - 0000000007eeeee0 (usable)
+I expect another hole for the Etherboot .text and heap segments,
+located at [01eeef70,01f00000). On entry to pxelinux (and while Linux
+is active), the hide_memory regions array includes
+[01eeef70,01f00000)
+[01eeef60,01eeef70)
+// as well as UNDI Data & Code
+Based on my understanding of the E820 adjustment code, I should get a
+memory region of [1f00000,7eeeee0).
+I've instrumented my Linux kernel to dump the E820 map as it is
+processed, and it looks like the E820 map I am getting has not been
+modified from the BIOS version.
+Any ideas on how to proceed?
+</file>
+<file>
+Date: Wed, 14 Jun 2006 15:12:16 +0100 (BST)
+From: Michael Brown <mbrown@fensystems.co.uk>
+X-X-Sender: mcb30@dolphin.home
+To: Alan Shieh <alancshieh@gmail.com>
+Cc: Etherboot <Etherboot-discuss@lists.sourceforge.net>
+Subject: Re: [Etherboot-discuss] E820 map
+In-Reply-To: <1a7e305d0606120120l39b78b49n610b4ab7c9c03e05@mail.gmail.com>
+Message-ID: <Pine.LNX.4.62.0606141509050.27611@dolphin.home>
+References: <1a7e305d0606120120l39b78b49n610b4ab7c9c03e05@mail.gmail.com>
+MIME-Version: 1.0
+Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
+On Mon, 12 Jun 2006, Alan Shieh wrote:
+> As discussed on IRC, my PXE booted Linux was not getting a E820 map
+> that reflected the resident PXE stack.
+>
+> I tracked down the problem for my Etherboot 5.2 snapshot. _hide_memory
+> only had 2 entries, one for the .text segment, and one for the heap.
+> However, the UNDI Code and Data segments are allocated from base
+> memory, which is not covered by either of these regions.
+>
+> So I fixed hide_etherboot() and _hide_memory to reflect the UNDI
+> segments, and now they are correctly omitted from the e820 map.
+>
+> However, I'm still wary of my e820 map:
+>
+> BIOS-e820: 0000000000000000 - 000000000009e000 (usable)
+> BIOS-e820: 0000000000100000 - 0000000007eeeee0 (usable)
+>
+> I expect another hole for the Etherboot .text and heap segments,
+> located at [01eeef70,01f00000). On entry to pxelinux (and while Linux
+> is active), the hide_memory regions array includes
+>
+> [01eeef70,01f00000)
+> [01eeef60,01eeef70)
+> // as well as UNDI Data & Code
+How much memory does this machine actually have?  The 0x07eeeee0 suggests
+a figure around the 128MB mark.  Etherboot should be relocating itself to
+somewhere near the top of this, yet 0x01eeef70 is around the 32MB mark.
+Something here doesn't add up.
+Michael
+</file>
+<file>
+Date: Wed, 14 Jun 2006 16:14:11 +0100 (BST)
+From: Michael Brown <mbrown@fensystems.co.uk>
+X-X-Sender: mcb30@dolphin.home
+To: Alan Shieh <alancshieh@gmail.com>
+Cc: Etherboot <Etherboot-discuss@lists.sourceforge.net>
+Subject: Re: [Etherboot-discuss] E820 map
+In-Reply-To: <1a7e305d0606140727r2cdc2576u527c082b5b39eef6@mail.gmail.com>
+Message-ID: <Pine.LNX.4.62.0606141611220.27611@dolphin.home>
+References: <1a7e305d0606120120l39b78b49n610b4ab7c9c03e05@mail.gmail.com>
+ <Pine.LNX.4.62.0606141509050.27611@dolphin.home>
+ <1a7e305d0606140727r2cdc2576u527c082b5b39eef6@mail.gmail.com>
+MIME-Version: 1.0
+Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
+On Wed, 14 Jun 2006, Alan Shieh wrote:
+>>> [01eeef70,01f00000)
+>>> [01eeef60,01eeef70)
+>>> // as well as UNDI Data & Code
+>>
+>> How much memory does this machine actually have?  The 0x07eeeee0 suggests
+>> a figure around the 128MB mark.  Etherboot should be relocating itself to
+>> somewhere near the top of this, yet 0x01eeef70 is around the 32MB mark.
+>> Something here doesn't add up.
+>
+> Yes, the machine has 128 MB.
+Thanks.  Can you add some debug statements to the relocation logic, to see
+how Etherboot ends up making the decision to relocate to the 32MB mark?
+For Etherboot 5.4 and below, the e820 map mangler can only truncate
+regions; it can't split them.  This can result in wasting huge amounts
+of memory space unless the region to be hidden is located near the end of
+an existing region.
+This is fixed in gpxe-0.5 (which can split regions), but that branch
+doesn't currently have a working PXE API and so is not much use for your
+tests.
+Michael
+</file>

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