Hi Bhupesh,
> -----Original Message-----
> > > I am working on the changes in the vmcoreinfo after the 52-bit VA
> > > changes from Steve were accepted in Linux 5.4-rc1 ("Support for 52-bit
> > > virtual addressing in kernel space”).
> >
> >
> > I don’t see a commit with this title in linux-stable ; Could you be a little more specific what
> file that was applied to ?
>
> You can have a look at the following commit (and dependencies) in
> Linus's tree (git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git)
> which introduced 52-bit kernel VAs for arm64 architecture:
>
> commit b6d00d47e81a49f6cf462518c10408f37a3e6785
> Author: Steve Capper <steve.capper@xxxxxxx>
> Date: Wed Aug 7 16:55:22 2019 +0100
>
> arm64: mm: Introduce 52-bit Kernel VAs
Thank you for working on this.
I've also had a look at them, and my understanding is that we need
in vmcoreinfo at least:
- TCR_EL1.T1SZ (almost equals to vabits_actual) to determine:
o PAGE_OFFSET
o whether the kernel has the "flipped" linear map and the others.
We need a fix to __pa() with it. (see the patch below)
- PA_BITS or MAX_PHYSMEM_BITS to determine:
o whether SPARSEMEM_EXTREME or not, in is_sparsemem_extreme()
o whether the kernel has 48-bit or 52-bit PA to switch
the calculation of pte-to-paddr. (this might be unnecessary?)
Is this right?
And wrote a very draft patch, which works on a 5.4-rc4 kernel that
I modified to have NUMBER(vabits_actual) and NUMBER(MAX_PHYSMEM_BITS),
with VA_BITS=48 config or VA_BITS=52 config running in 48-bit mode.
https://github.com/k-hagio/makedumpfile/commit/fd9d86ea05b38e9edbb8c0ac3ebd612d5d485df3
(I don't intend to export them as they are, it's just for an experiment.
And no support for --mem-usage option, "real" 52-bit PA, and so on.)
As for MAX_PHYSMEM_BITS, I don't stick to export it for all architectures,
although I told you that it would be better to do so in the past.
If it's hard to do so, it's fine with me to export it or something similar
only for arm64 for now..
Your thoughts?
Thanks,
Kazu
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