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Linux x86/x86_64 Will Now Always Reserve The First 1MB Of RAM

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  • Linux x86/x86_64 Will Now Always Reserve The First 1MB Of RAM

    Phoronix: Linux x86/x86_64 Will Now Always Reserve The First 1MB Of RAM

    The Linux x86/x86_64 kernel code already had logic in place for reserving portions of the first 1MB of RAM to avoid the BIOS or kernel potentially clobbering that space among other reasons while now Linux 5.13 is doing away with that "wankery" and will just unconditionally always reserve the first 1MB of RAM...

    https://www.phoronix.com/scan.php?pa...ys-Reserve-1MB

  • #2
    bios and boot leader is always a joke for me and old one too

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    • #3
      I did have one unusual system, a Toshiba Libretto 70CT (Pentium 120 MMX, 32MB RAM!) where the PCMCIA slot wouldn't work following the initial change to reserve the first 1MB some years ago. I had to bisect the kernel to figure this out, which took a while. In the end, I just reverted the commit for my builds. I sold it on eBay years ago though so not a problem for me any more.

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      • #4
        This may have implications for embedded systems. For example, many router SOC only have 16 or 32 MB and one megabyte less can make a difference between a usable system and OOM at boot.

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        • #5
          Originally posted by turboNOMAD View Post
          This may have implications for embedded systems. For example, many router SOC only have 16 or 32 MB and one megabyte less can make a difference between a usable system and OOM at boot.
          These are usually not x86 based.

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          • #6
            Originally posted by Aryma View Post
            bios and boot leader is always a joke for me and old one too
            Because you want a BIOS which knows about every possible file system and operating system in existence, past, present and future?

            There is no joke here. The joke is perhaps in BIOSes with graphical interfaces and mouse control, but the separation of BIOS and bootloader is rather smart.

            If you do not like bootloaders then just use one that is invisible to you. There is more than GRUB.
            Last edited by sdack; 06 June 2021, 10:41 AM.

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            • #7
              Originally posted by turboNOMAD View Post
              This may have implications for embedded systems. For example, many router SOC only have 16 or 32 MB and one megabyte less can make a difference between a usable system and OOM at boot.
              It isn't an issue for newer hardware, as newer hardware has far more RAM than that, with 128-512MB being commonplace. The low-end hardware you speak of is not sold in today's markets and hasn't been used for a long time.

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              • #8
                the kernel is playing it safe and just always reserving the first 1MB of RAM so it will not get clobbered by the kernel.
                Should that be BIOS ?

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                • #9
                  Originally posted by TheLexMachine View Post
                  It isn't an issue for newer hardware, as newer hardware has far more RAM than that, with 128-512MB being commonplace. The low-end hardware you speak of is not sold in today's markets and hasn't been used for a long time.
                  Give it a couple of decades, and we'll see a commit to reserve the first 1 Gigabyte of RAM. You won't care because your laptop has 4 TB of RAM. We we chuckle with nostalgia at the days when RAM was discussed in Megabytes.

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                  • #10
                    Originally posted by project_phelius View Post
                    Should that be BIOS ?
                    No. So what they mean by reserving it is that the kernel will never use memory in the 1st MB either for itself or giving it to user-space applications. The problem they are solving with it is that some BIOS'es and other shitty system firmware will in some cases use that memory, leading to corruption if both the firmware and the OS think they can use it at the same time.

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