[PATCH v3 0/5] Add pmem node for preserving distro ISO's

[Sughosh Ganu]

On Fri, 24 Jan 2025 at 17:10, Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> Heinrich, Tobias
>
> There's a slight problem that I forgot when commenting v2.
>
> Heinrich's idea of plugging this into blkmap is eventually the right
> thing to do.
>
> However, when I started coding this I only added the pmem memory as
> 'reserved' in the DT hoping that would work.
> Unfortunately, this depends on a kernel config option. I've managed to
> track down the problem here[0], but I haven't found time to test it
> properly and send it upstream.
> So for this feature to work reliably we *need* to remove the memory
> map we hand over to the OS.
>
> Since using EFI memmap function into the blkmap code makes no sense,
> can we perhaps merge v2 (or a variant of it), which only targets EFI,
> with an explanation of *why* while I try to sort out the kernel issue?

If it has been decided to go with the approach taken in V2, I will
send an updated series which incorporates the other nits that Heinrich
had on the patches. Those were handled in this version.

-sughosh

>
>
> [0] https://git.linaro.org/people/ilias.apalodimas/net-next.git/commit/?h=main
>
> Thanks
> /Ilias
>
> On Mon, 20 Jan 2025 at 12:51, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
> >
> >
> > When installing a distro via EFI HTTP boot some OS installers expect
> > the .iso image to be preserved and treat it as a "CDROM" to install
> > packages.
> >
> > This is problematic in EFI, since U-Boot mounts the image, starts the
> > installer, and eventually calls ExitBootServices. At that point the
> > image U-Boot mounted disappears. Some distros don't care and download
> > the missing packages from a web archive, while others halt the
> > installation complaining they can't find certain packages.
> >
> > If the firmware uses ACPI, this is supported by using NFIT which
> > provides NVDIMM ramdisks to the OS and preserves the image.
> > We don't have anything in place for Device Trees though. Since DT
> > supports persistent memory nodes (pmem) use those and preserve the
> > .iso for installers.
> >
> > The issue can be reproduced by attempting an EFI HTTP boot with Ubuntu
> > live server ISO, or a Rocky Linux ISO. The installation would fail
> > with the failure to locate certain packages.
> >
> > The earlier version had aligned the addition of pmem nodes with the
> > EFI HTTP boot feature. This has been changed, based on a review
> > comment from Heinrich to instead be done by looping through the memory
> > based blkmamp devices.
> >
> > Changes since V2:
> > * Fix a checkpatch error for putting a blank line after a function
> > * Use blkmap device based scanning for adding the pmem nodes
> >
> >
> >
> > Ilias Apalodimas (2):
> >   efi_loader: add a function to remove memory from the EFI map
> >   efi_loader: preserve installer images in pmem
> >
> > Masahisa Kojima (1):
> >   fdt: add support for adding pmem nodes
> >
> > Sughosh Ganu (2):
> >   blkmap: store type of blkmap device in corresponding structure
> >   blkmap: add pmem nodes for blkmap mem mapping devices
> >
> >  boot/fdt_support.c            |  40 ++++++++++++-
> >  boot/image-fdt.c              |   9 +++
> >  cmd/blkmap.c                  |  16 ++++--
> >  drivers/block/blkmap.c        |  90 +++--------------------------
> >  drivers/block/blkmap_helper.c |  47 +++++++++++++++-
> >  include/blkmap.h              | 103 +++++++++++++++++++++++++++++++++-
> >  include/efi_loader.h          |  11 ++--
> >  include/fdt_support.h         |  13 +++++
> >  lib/efi_loader/efi_bootmgr.c  |  22 ++++++--
> >  lib/efi_loader/efi_memory.c   |  51 ++++++++++++-----
> >  lib/lmb.c                     |   4 +-
> >  test/dm/blkmap.c              |  16 +++---
> >  12 files changed, 302 insertions(+), 120 deletions(-)
> >
> > --
> > 2.34.1
> >
> >