Re: [RFC PATCH 2/4] of: Add a common kexec FDT setup function

[Lakshmi Ramasubramanian]

On 12/11/20 6:17 PM, Thiago Jung Bauermann wrote:
> Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx> writes:
>
> > On 12/11/20 2:10 PM, Rob Herring wrote:
> >
> > Hi Rob,
> >
> > > Both arm64 and powerpc do essentially the same FDT /chosen setup for
> > > kexec. We can simply combine everything each arch does. The differences
> > > are either omissions that arm64 should have or additional properties
> > > that will be ignored.
> > > The differences relative to the arm64 version:
> > > - If /chosen doesn't exist, it will be created (should never happen).
> > > - Any old dtb and initrd reserved memory will be released.
> > > - The new initrd and elfcorehdr are marked reserved.
> > > - "linux,booted-from-kexec" is set.
> > > The differences relative to the powerpc version:
> > > - "kaslr-seed" and "rng-seed" may be set.
> > > - "linux,elfcorehdr" is set.
> > > - Any existing "linux,usable-memory-range" is removed.
> > > Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
> > > ---
> > > This could be taken a step further and do the allocation of the new
> > > FDT. The difference is arm64 uses vmalloc and powerpc uses kmalloc. The
> > > arm64 version also retries with a bigger allocation. That seems
> > > unnecessary.
> > > ---
> > >    drivers/of/Makefile |   1 +
> > >    drivers/of/kexec.c  | 228 ++++++++++++++++++++++++++++++++++++++++++++
> > >    include/linux/of.h  |   5 +
> > >    3 files changed, 234 insertions(+)
> > >    create mode 100644 drivers/of/kexec.c
> > > diff --git a/drivers/of/Makefile b/drivers/of/Makefile
> > > index 6e1e5212f058..8ce11955afde 100644
> > > --- a/drivers/of/Makefile
> > > +++ b/drivers/of/Makefile
> > > @@ -13,5 +13,6 @@ obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o
> > >    obj-$(CONFIG_OF_RESOLVE)  += resolver.o
> > >    obj-$(CONFIG_OF_OVERLAY) += overlay.o
> > >    obj-$(CONFIG_OF_NUMA) += of_numa.o
> > > +obj-$(CONFIG_KEXEC_FILE) += kexec.o
> >
> > For the functions moved from powerpc & arm64 to "drivers/of/kexec.c" in this
> > patch, compiling kexec.c when CONFIG_KEXEC_FILE is enabled is fine. But when
> > more functions (such as remove_ima_buffer()) are moved to this file, Makefile
> > needs to be updated for other ima kexec related CONFIGs.
>
> IMA kexec is only available if CONFIG_KEXEC_FILE is enabled, so I don't
> understand what problem you are seeing.

delete_fdt_mem_rsv() and setup_fdt() functions are defined when 
CONFIG_KEXEC_FILE is enabled. So there is no problem with this patch as 
such.

I was thinking when other arch independent functions such as 
do_get_kexec_buffer() and remove_ima_buffer() are moved to 
"drivers/of/kexec.c", they need to be defined only when 
CONFIG_HAVE_IMA_KEXEC is enabled.

If CONFIG_HAVE_IMA_KEXEC is enabled, CONFIG_KEXEC_FILE is also enabled. 
So there shouldn't be a problem moving those functions to 
"drivers/of/kexec.c". You are right Thiago. Thanks.

 -lakshmi