[RFC PATCH v2 00/48] Make U-Boot memory reservations coherent

[Simon Glass]

Hi Sughosh,

On Mon, 22 Jul 2024 at 18:37, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
>
> On Mon, 22 Jul 2024 at 23:03, Tom Rini <trini at konsulko.com> wrote:
> >
> > On Mon, Jul 22, 2024 at 11:58:18AM +0530, Sughosh Ganu wrote:
> > > On Mon, 8 Jul 2024 at 19:32, Tom Rini <trini at konsulko.com> wrote:
> > > >
> > > > On Thu, Jul 04, 2024 at 01:04:56PM +0530, Sughosh Ganu wrote:
> > > >
> > > > > The aim of this patch series is to fix the current state of
> > > > > incoherence between modules when it comes to memory usage. The primary
> > > > > issue that this series is trying to fix is that the EFI memory module
> > > > > which is responsible for allocating and freeing memory, does not have
> > > > > any visibility of the memory that is being used by the LMB
> > > > > module. This is further complicated by the fact that the LMB
> > > > > allocations are caller specific -- the LMB memory map is not global
> > > > > nor persistent. This means that the memory "allocated" by the LMB
> > > > > module might be relevant only for a given function. Hence one of the
> > > > > requirements for making the memory usage visible across modules is to
> > > > > make LMB allocations persistent and global, and then have means to
> > > > > communicate the use of memory across modules.
> > > > >
> > > > > The first set of patches in this series work on making the LMB memory
> > > > > map persistent and global. This is being done keeping in mind the
> > > > > usage of LMB memory by platforms where the same memory region can be
> > > > > used to load multiple different images. What is not allowed is to
> > > > > overwrite memory that has been allocated by the other module,
> > > > > currently the EFI memory module. This is being achieved by introducing
> > > > > a new flag, LMB_NOOVERWRITE, which represents memory which cannot be
> > > > > re-requested once allocated.
> > > > >
> > > > > A review comment on the earlier version was to do away with the static
> > > > > arrays for the LMB lists of free and used memory. This version
> > > > > uses the alloced list data structure for the LMB lists.
> > > > >
> > > > > The second set of patches are making changes to the EFI memory module
> > > > > to make use of the LMB functions to allocate and free memory. A
> > > > > *_flags() version of LMB API's has been introduced for the same. The
> > > > > earlier version was using notification mechanism from both LMB and EFI
> > > > > modules to maintain memory coherence. This version makes use of the
> > > > > LMB API functions for the memory allocations. This is based on review
> > > > > comments of EFI maintainers.
> > > >
> > > > On am64x_evm_a53, the last test in test/py/tests/test_net_boot.py fails
> > > > due to:
> > > > ...
> > > > TFTP from server 192.168.116.10; our IP address is 192.168.116.23
> > > > Filename 'pxelinux.cfg/default-arm-k3'.
> > > > Load address: 0x80100000
> > > > Loading: ##################################################  64 Bytes
> > > >          8.8 KiB/s
> > > > done
> > > > Bytes transferred = 64 (40 hex)
> > > >   1  pxe          ready   ethernet     0  port at 1.bootdev.0          extlinux/extlinux.conf
> > > > ** Booting bootflow 'port at 1.bootdev.0' with pxe
> > > > Retrieving file: pxelinux.cfg/default-arm
> > > > am65_cpsw_nuss_port ethernet at 8000000port@1: K3 CPSW: rflow_id_base: 16
> > > > link up on port 1, speed 1000, full duplex
> > > > Using ethernet at 8000000port@1 device
> > > > TFTP from server 192.168.116.10; our IP address is 192.168.116.23
> > > > Filename 'pxelinux.cfg/default-arm'.
> > > >
> > > > TFTP error: trying to overwrite reserved memory...
> > > > Couldn't retrieve pxelinux.cfg/default-arm
> > >
> > > So this seems to be failing because the address used to load the pxe
> > > config file seems to be overlapping with an already reserved region of
> > > memory. Can you please check if modifying the address works?
> >
> > I'm not sure what address you're thinking of modifying but, this isn't
> > overwriting U-Boot itself so it's a case that needs to work.
>
> Can you please print the lmb memory map through bdinfo and share it
> with me. That will give some info on what is causing the issue. Thing
> is, with this patchset, if there is another reservation with a
> different flag(like LMB_NOMAP, LMB_NOOVERWRITE), this would cause the
> load to fail.

I too am interested in what it might be. Scripts in general can load
things where they want, so we need to be careful.

Also, as mentioned I would really like to clean up the 'EFI'
'allocations' so that they only happen when booting an EFI payload. I
am not too sure what the current state is, but I will see if I can
take a look.

Regards,
SImon