Messages in this thread | | | Date | Tue, 17 Nov 1998 22:05:48 +0100 (MET) | From | Cyrille Chepelov <> | Subject | Re: i386 boot & mm gurus' advice needed (int 0x15/0xE820 support) |
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On 16 Nov 1998, H. Peter Anvin wrote:
> Basically. The memory from 0x600 to 0xfff should be safe to use; the > kernel doesn't trash the zero-page because emulators need the > BIOS-info, but the BIOS-info ends at 0x5ff. Other than that, most of > the communication between setup and the kernel is done by overwriting > the boot sector at 0x90000, there may be enough space there after the > command line buffer.
I'll try something along these lines (probably tomorrow, perhaps later this evening).
> Note that there are no less than four (4) BIOS interfaces to query > memory: INT 15h, AH=88h (this is the infamous 64MB limit, but is all > that is available on some old machines); INT 15h AX=E801h (currently > used on newer kernels), INT 15h AX=E802h (not widely used), and INT > 15h AX=E820h (the latest whiz-bang call.) Since the latter is a > proper superset of the others, the right thing to do is probably to > make setup.S try the different BIOS queries, but pass the data to the > kernel in a single format (compatible with INT 15h AX=E820h).
saw that. E802 looks to be deprecated. My patch as I sample-released it uses E820 if available, and falls back on the previous behaviour (E801 if possible, 88 instead) if E820 returns an error or CONFIG_NO_QSAM. Except with the fact that my choice of 16/32bit communication buffer wasn't that wise, I haven't got a report that this patch broke anything (better, it should improve the situation for people, willing or not, who have memory holes ; finally, it is a good prerequisite for working on ACPI whithout cheating with bootparam "mem=<whatever-1>M". I'm not sure however whether this would warrant an inclusion in 2.2 ; I've been always targeting self-education and perhaps 2.3 -- not my call anyways.)
-- Cyrille
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