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It Turns Out Windows Unconditionally Reserves The First 1MB Of RAM, Linux Was Just Late To Do So

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  • It Turns Out Windows Unconditionally Reserves The First 1MB Of RAM, Linux Was Just Late To Do So

    Phoronix: It Turns Out Windows Unconditionally Reserves The First 1MB Of RAM, Linux Was Just Late To Do So

    Sent in last weekend to the Linux 5.13 kernel was the change so Linux x86/x86_64 will always reserve the first 1MB of RAM in order to avoid corruption issues with some BIOS and frame-buffers sometimes fiddling with that lowest portion of system memory. While the thought was reserving that first 1MB unconditionally was a bit onerous and that perhaps Windows has some way of determining how much low memory area to reserve, it turns out Windows has been employing this same behavior for years...

    https://www.phoronix.com/scan.php?pa...-First-1MB-RAM

  • #2
    Windows: Doing it correctly 11 years ago what Linux only does now.

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    • #3
      It should have been obvious even without MS acknowledgement: that's why Windows never crashes.

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      • #4
        Originally posted by Sonadow View Post
        Windows: Doing it correctly 11 years ago what Linux only does now.
        That's not the correct solution. It's just the lesser of the evils.

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        • #5
          Originally posted by Sonadow View Post
          Windows: Doing it correctly 11 years ago what Linux only does now.
          This is something I must have missed in the PC specification. Ah yes here it is "A OS Kernel always have to reserve and leave alone the first 1MB of ram because a buggy Firmware may use that", the Linux People must have clearly missed this and the Windows people have done it correct.
          1:0 For the Windows People.

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          • #6
            This is yet another case of when dealing with low level system interfaces, it's best to do whatever Windows does (as that's all firmware programmers tend to test) rather than what the spec says.

            There was another similar issue a few years ago where doing what Windows does fixed reboot hangs on some systems: https://mjg59.livejournal.com/137313.html

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            • #7
              Unfortunately most BIOS code is of the poorest software quality, as you can see when navigating through the BIOS menu, or when upgrading it, and the untyped binary BLOB representing the settings of the previous version cannot be imported. It is hardly surprising they think they can command over the real mode address space as they wish.

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              • #8
                Originally posted by Alexmitter View Post

                This is something I must have missed in the PC specification. Ah yes here it is "A OS Kernel always have to reserve and leave alone the first 1MB of ram because a buggy Firmware may use that", the Linux People must have clearly missed this and the Windows people have done it correct.
                1:0 For the Windows People.
                Mmmmm... I think there is a big mistake in your comment...

                I think it should be "An OS Kernel..."

                (it's only a joke ;-) )
                Last edited by rastersoft; 09 June 2021, 07:46 AM.

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                • #9
                  Originally posted by Sonadow View Post
                  Windows: Doing it correctly 11 years ago what Linux only does now.
                  You need to learn how to bait better.

                  Comment


                  • #10
                    Originally posted by Sonadow View Post
                    Windows: Doing it correctly 11 years ago what Linux only does now.
                    The correct way would be for both Windows and Linux to refuse to boot if the BIOS corrupts the memory. That would lead to an actual fix of the root cause....

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