In order to see the SPD (detailed memory information) data, the user currently has to manually load the needed kernel driver. Which driver to load depends on the memory type. Depending on the driver user, the devices may even have to be instantiated manually and this is a non-trivial multi-step task. Plus you need to be root to do it.

I would like to attempt to automatize all this at least in the most common and simple cases like Intel x86 desktop. The idea would be to figure out the memory type and the I2C address of the SPD EEPROMs based on DMI data. If the DMI data is of good quality then it should be possible to automatically figure out which driver to use and to instantiate the devices at boot time.

If this works then running "decode-dimms" (or any other equivalent tool) should just work after boot without any preparatory work, for all users.

I plan to start implementing this for DDR3 memory and the i2c-i801 SMBus controller driver because that's what I have on my workstation. If it works, doing the same for DDR4 shouldn't be too difficult. Once this works for the i2c-i801, it should be pretty trivial to do the same with other SMBus controller drivers, for example i2c-piix4.

Excluded from the scope are large server systems with multiple SMBus controllers or multiplexed SMBus. Also excluded are OF/DT systems as I would expect SPD EEPROMs to be declared in the device tree so they would already be instantiated without further effort.

Looking for hackers with the skills:

i2c-tools kernel smbus dmi

This project is part of:

Hack Week 18

Activity

  • about 5 years ago: jdelvare started this project.
  • almost 6 years ago: a_faerber liked this project.
  • almost 6 years ago: jdelvare added keyword "i2c-tools" to this project.
  • almost 6 years ago: jdelvare added keyword "kernel" to this project.
  • almost 6 years ago: jdelvare added keyword "smbus" to this project.
  • almost 6 years ago: jdelvare added keyword "dmi" to this project.
  • almost 6 years ago: jdelvare originated this project.

  • Comments

    • jdelvare
      about 4 years ago by jdelvare | Reply

      For the record, this hack week project was successful. Relevant upstream kernel commits:

      commit 9e0afe3910ff7e5493c5d8ebe3b499994b5e0272
      Author: Jean Delvare 
      Date:   Tue Dec 3 11:20:37 2019 +0100
      
          firmware: dmi: Remember the memory type
      
      commit 7c2378800cf7ac87e2663afa7f39d102871f0c28
      Author: Jean Delvare 
      Date:   Tue Dec 3 11:20:37 2019 +0100
      
          firmware: dmi: Add dmi_memdev_handle
      
      commit 5ace60859e84113b7a185c117fbf2c429d381b59
      Author: Jean Delvare 
      Date:   Mon Mar 16 11:22:24 2020 +0100
      
          i2c: smbus: Add a way to instantiate SPD EEPROMs automatically
      
      commit 01590f361e94a01e9b9868fa81d4079d255c681f
      Author: Jean Delvare 
      Date:   Mon Mar 16 11:24:48 2020 +0100
      
          i2c: i801: Instantiate SPD EEPROMs automatically
      

      So the feature is supported since kernel v5.8. Next step is to extend support to systems with 5-8 memory slots (still on a single SMBus segment), and to add support to other SMBus controller drivers.

    Similar Projects

    Create DRM drivers for VESA and EFI framebuffers by tdz

    Description

    We already have simpledrm for firmware framebuffers. But the driver is originally for ARM boards, not PCs. It is already overloaded with code to support both use cases. At the same time it is missing possible features for VESA and EFI, such as palette modes or EDID support. We should have DRM drivers for VESA and EFI interfaces. The infrastructure exists already and initial drivers can be forked from simpledrm.

    Goals

    • Initially, a bare driver for VESA or EFI should be created. It can take functionality from simpledrm.
    • Then we can begin to add additional features. The boot loader can provide EDID data. With VGA hardware, VESA can support paletted modes or color management. Example code exists in vesafb.


    Create a DRM driver for VGA video cards by tdz

    Yes, those VGA video cards. The goal of this project is to implement a DRM graphics driver for such devices. While actual hardware is hard to obtain or even run today, qemu emulates VGA output.

    VGA has a number of limitations, which make this project interesting.

    • There are only 640x480 pixels (or less) on the screen. That resolution is also a soft lower limit imposed by DRM. It's mostly a problem for desktop environments though.
    • Desktop environments assume 16 million colors, but there are only 16 colors with VGA. VGA's 256 color palette is not available at 640x480. We can choose those 16 colors freely. The interesting part is how to choose them. We have to build a palette for the displayed frame and map each color to one of the palette's 16 entries. This is called dithering, and VGA's limitations are a good opportunity to learn about dithering algorithms.
    • VGA has an interesting memory layout. Most graphics devices use linear framebuffers, which store the pixels byte by byte. VGA uses 4 bitplanes instead. Plane 0 holds all bits 0 of all pixels. Plane 1 holds all bits 1 of all pixels, and so on.

    The driver will probably not be useful to many people. But, if finished, it can serve as test environment for low-level hardware. There's some interest in supporting old Amiga and Atari framebuffers in DRM. Those systems have similar limitations as VGA, but are harder to obtain and test with. With qemu, the VGA driver could fill this gap.

    Apart from the Wikipedia entry, good resources on VGA are at osdev.net and FreeVGA


    Contributing to Linux Kernel security by pperego

    Description

    A couple of weeks ago, I found this blog post by Gustavo Silva, a Linux Kernel contributor.

    I always strived to start again into hacking the Linux Kernel, so I asked Coverity scan dashboard access and I want to contribute to Linux Kernel by fixing some minor issues.

    I want also to create a Linux Kernel fuzzing lab using qemu and syzkaller

    Goals

    1. Fix at least 2 security bugs
    2. Create the fuzzing lab and having it running

    The story so far

    • Day 1: setting up a virtual machine for kernel development using Tumbleweed. Reading a lot of documentation, taking confidence with Coverity dashboard and with procedures to submit a kernel patch
    • Day 2: I read really a lot of documentation and I triaged some findings on Coverity SAST dashboard. I have to confirm that SAST tool are great false positives generator, even for low hanging fruits.
    • Day 3: Working on trivial changes after I read this blog post: https://www.toblux.com/posts/2024/02/linux-kernel-patches.html. I have to take confidence with the patch preparation and submit process yet.
      • First trivial patch sent: using strtruefalse() macro instead of hard-coded strings in a staging driver for a lcd display
      • Fix for a dereference before null check issue discovered by Coverity (CID 1601566) https://scan7.scan.coverity.com/#/project-view/52110/11354?selectedIssue=1601566
    • Day 4: Triaging more issues found by Coverity.
      • The patch for CID 1601566 was refused. The check against the NULL pointer was pointless so I prepared a version 2 of the patch removing the check.
      • Fixed another dereference before NULL check in iwlmvmparsewowlaninfo_notif() routine (CID 1601547). This one was already submitted by another kernel hacker :(
    • Day 5: Wrapping up. I had to do some minor rework on patch for CID 1601566. I found a stalker bothering me in private emails and people I interacted with me, advised he is a well known bothering person. Markus Elfring for the record.
    • Wrapping up: being back doing kernel hacking is amazing and I don't want to stop it. My battery pack is completely drained but changing the scope gave me a great twist and I really want to feel this energy not doing a single task for months.

      I failed in setting up a fuzzing lab but I was too optimistic for the patch submission process.

    The patches

    1


    Improve UML page fault handler by ptesarik

    Description

    Improve UML handling of segmentation faults in kernel mode. Although such page faults are generally caused by a kernel bug, it is annoying if they cause an infinite loop, or panic the kernel. More importantly, a robust implementation allows to write KUnit tests for various guard pages, preventing potential kernel self-protection regressions.

    Goals

    Convert the UML page fault handler to use oops_* helpers, go through a few review rounds and finally get my patch series merged in 6.14.

    Resources

    Wrong initial attempt: https://lore.kernel.org/lkml/20231215121431.680-1-petrtesarik@huaweicloud.com/T/


    Linux on Cavium CN23XX cards by tsbogend

    Before Cavium switched to ARM64 CPUs they developed quite powerful MIPS based SOCs. The current upstream Linux kernel already supports some Octeon SOCs, but not the latest versions. Goal of this Hack Week project is to use the latest Cavium SDK to update the Linux kernel code to let it running on CN23XX network cards.