Re: [PATCH v3 07/17] arm64, hibernate: move page handling function to new trans_pgd.c

[Pavel Tatashin]

On Fri, Sep 6, 2019 at 11:18 AM James Morse <james.morse@xxxxxxx> wrote:
>
> Hi Pavel,
>
> On 21/08/2019 19:31, Pavel Tatashin wrote:
> > Now, that we abstracted the required functions move them to a new home.
> > Later, we will generalize these function in order to be useful outside
> > of hibernation.
>
> > diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
> > new file mode 100644
> > index 000000000000..00b62d8640c2
> > --- /dev/null
> > +++ b/arch/arm64/mm/trans_pgd.c
> > @@ -0,0 +1,211 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +/*
> > + * Copyright (c) 2019, Microsoft Corporation.
> > + * Pavel Tatashin <patatash@xxxxxxxxxxxxxxxxxxx>
>
> Hmmm, while line-count isn't a useful metric: this file contains 41% of the code that was
> in hibernate.c, but has stripped the substantial copyright-pedigree that the hibernate
> code had built up over the years.
> (counting lines identified by 'cloc' as code, not comments or blank)
>
> If you are copying or moving a non trivial quantity of code, you need to preserve the
> copyright. Something like 'Derived from the arm64 hibernate support which has:'....

I will do that.  The copyright thing was meant to appear in
"generalization" patch that comes later, where I unified most of the
code to be symmetric.
So, I will add it there, and also do the derived message that you suggested.

>
>
> > + */
> > +
> > +/*
> > + * Transitional tables are used during system transferring from one world to
> > + * another: such as during hibernate restore, and kexec reboots. During these
> > + * phases one cannot rely on page table not being overwritten.
>
> I think you need to mention that hibernate and kexec are rewriting memory, and may
> overwrite the live page tables, therefore ...

Will add, thank you.

Pasha