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From: "Alexander van Heukelum" <heukelum@fastmail.fm>
To: "H. Peter Anvin" <hpa@zytor.com>, "Andi Kleen" <ak@suse.de>
Cc: "Ingo Molnar" <mingo@elte.hu>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"LKML" <linux-kernel@vger.kernel.org>,
	"Alexander van Heukelum" <heukelum@mailshack.com>
Subject: Re: [PATCH] Fix alignment of early reservation for EBDA
Date: Mon, 25 Feb 2008 17:54:38 +0100	[thread overview]
Message-ID: <1203958478.20033.1239002461@webmail.messagingengine.com> (raw)
In-Reply-To: <47C22568.1010405@zytor.com>

On Sun, 24 Feb 2008 18:18:16 -0800, "H. Peter Anvin" <hpa@zytor.com>
said:
> Alexander van Heukelum wrote:
> > early res: 3 [9f000-9ffff] EBDA
> > 
> > Is it really necessary to force the allocation to a page boundary?
> 
> It is, but that rounding gets done in reserve_bootmem() anyway, so there 
> is no need for the arch-specific code to do it.
> 
> The 32-bit EBDA code hard-codes a size of 4K, which is probably equally 
> wrong; my gut feel is that the right thing to do is to reserve from the 
> EBDA up to the 640K mark (some BIOSes use an area like that for SMM 
> stuff), possibly with some sanity checking.

Then, how about reserving everything from the end of conventional memory
up to the 1Mb mark? Like this:

/*
 * The BIOS places the EBDA/XBDA at the top of conventional
 * memory, and usually decreases the reported amount of
 * conventional memory (int 0x12) too.
 */
static __init void reserve_ebda(void)
{
        unsigned int lowmem, ebda_addr;

        /* end of low (conventional) memory */
        lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES);
        lowmem <<= 10;

        /* start of EBDA area */
        ebda_addr = *(unsigned short *)__va(BIOS_EBDA_SEGMENT);
        ebda_addr <<= 4;

        /* Fixup: bios puts an EBDA in the top 64K segment */
        /* of conventional memory, but does not adjust lowmem. */
        if ((lowmem - ebda_addr) <= 0x10000)
                lowmem = ebda_addr;

        /* Fixup: bios does not report an EBDA at all. */
        /* Some old Dells seem to need 4k anyhow (bugzilla 2990) */
        if ((ebda_addr == 0) && (lowmem >= 0x9f000))
                lowmem = 0x9f000;

        /* Paranoia: should never happen, but... */
        if (lowmem >= 0x100000)
                lowmem = 0xa0000;

        /* reserve all memory between lowmem and the 1MB mark */
        reserve_early(lowmem, 0x100000, "BIOS reserved");
}

Greetings,
    Alexander
-- 
  Alexander van Heukelum
  heukelum@fastmail.fm

-- 
http://www.fastmail.fm - Choose from over 50 domains or use your own


  reply	other threads:[~2008-02-25 16:54 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-24 17:46 Alexander van Heukelum
2008-02-24 19:27 ` Andi Kleen
2008-02-24 19:41 ` Ingo Molnar
2008-02-24 20:53   ` Alexander van Heukelum
2008-02-25  2:18 ` H. Peter Anvin
2008-02-25 16:54   ` Alexander van Heukelum [this message]
2008-02-25 17:01     ` Ingo Molnar
2008-02-25 18:07       ` [PATCH] reserve_early end-of-conventional-memory to 1MB Alexander van Heukelum
2008-02-25 18:13         ` H. Peter Anvin
2008-02-25 19:46           ` Alexander van Heukelum
2008-02-25 21:17             ` H. Peter Anvin
2008-02-26  9:30             ` Ingo Molnar
2008-02-27 14:26               ` Andi Kleen
2008-02-27 14:38               ` [PATCH] reserve_early end-of-conventional-memory to 1MB II - some numbers to put it into perspective Andi Kleen
2008-02-27 16:44                 ` H. Peter Anvin
2008-02-27 20:01                 ` Alexander van Heukelum
2008-02-28 13:13         ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit Alexander van Heukelum
2008-02-28 13:28           ` [RFC] use realmode code to reserve end-of-conventional-memory to 1MB Alexander van Heukelum
2008-02-28 21:12             ` Ian Campbell
2008-02-28 21:14               ` H. Peter Anvin
2008-02-28 23:16                 ` Ian Campbell
2008-02-29 20:00                   ` Ingo Molnar
2008-03-04 11:41                   ` Mark McLoughlin
2008-03-04 14:33                     ` Ingo Molnar
2008-03-04 15:12                       ` Ian Campbell
2008-03-04 15:13                       ` Jeremy Fitzhardinge
2008-03-04 15:25                         ` Ingo Molnar
2008-03-04 16:02                           ` Jeremy Fitzhardinge
2008-03-04 16:15                             ` Ingo Molnar
2008-03-04 16:15                       ` Mark McLoughlin
2008-03-04 16:23                         ` Ingo Molnar
2008-03-04 17:44                   ` Jeremy Fitzhardinge
2008-03-05 15:59                   ` Eduardo Habkost
2008-03-05 16:08                     ` H. Peter Anvin
2008-03-05 16:53                       ` Eduardo Habkost
2008-03-05 17:28                         ` H. Peter Anvin
2008-03-05 17:28                           ` Jeremy Fitzhardinge
2008-03-05 17:38                             ` H. Peter Anvin
2008-03-05 16:38                     ` Jeremy Fitzhardinge
2008-03-05 17:27                       ` H. Peter Anvin
2008-02-28 21:09           ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit Ian Campbell
2008-02-29 11:49             ` Alexander van Heukelum
2008-02-29 17:14               ` Mark McLoughlin
2008-02-29 18:38                 ` Alexander van Heukelum
2008-02-29 18:44                   ` H. Peter Anvin
2008-02-29 18:56                     ` Alexander van Heukelum
2008-02-29 22:06                   ` Mark McLoughlin
2008-02-29 22:26                     ` Alexander van Heukelum
2008-03-01 16:09                     ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit v2 Alexander van Heukelum
2008-03-01 16:12                       ` [PATCH] reserve end-of-conventional-memory to 1MB on 64-bit add-on Alexander van Heukelum
2008-03-04 11:44                       ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit v2 Mark McLoughlin
2008-03-04 13:31                         ` Alexander van Heukelum
2008-03-04 14:49                         ` Ingo Molnar
2008-03-04 15:16                           ` Mark McLoughlin
2008-03-04 15:24                             ` Ingo Molnar
2008-03-04 15:18                         ` Jeremy Fitzhardinge
2008-03-04 16:51                           ` Alexander van Heukelum
2008-03-04 17:05                             ` H. Peter Anvin
2008-03-04 17:11                             ` Jeremy Fitzhardinge
2008-03-04 18:57                               ` [PATCH] reserve end-of-conventional-memory to 1MB, 32-bit, use paravirt_enabled Alexander van Heukelum
2008-03-04 19:12                                 ` [PATCH] reserve end-of-conventional-memory to 1MB, 64-bit, " Alexander van Heukelum
2008-02-27 14:25     ` [PATCH] Fix alignment of early reservation for EBDA Andi Kleen

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