Hi Bhupesh,
OK, thanks for letting me know that in your holidays. Have good ones.
I just thought that it might be good to share our understanding before
posting a kernel patch so that I can do something to support you if
need be.
Hi John,
You see that error with my test patch, which is only for testing though,
as I wrote below
> > 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),
that patch requires a kernel fix to have these in vmcoreinfo.
Did you try it?
Thanks,
Kazu
> -----Original Message-----
> Hi Kazu,
>
> Sorry for top posting, but I am on leave for Diwali Holidays and will
> return to the office in a couple of days.
>
> I have the solution/patchset ready and I just need to finish the
> commit messages to make sure they are self-explanatory for upstream
> acceptance.
>
> I will try to post them and also answer your email in detail when I
> return back from holidays.
>
> Thanks for your patience.
>
> Regards,
> Bhupesh
>
> (Sent from my Android Phone)
>
> On Tue, Oct 29, 2019 at 2:23 AM Kazuhito Hagio <k-hagio@xxxxxxxxxxxxx> wrote:
> >
> > 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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