Re: [PATCH v3 06/17] arm64, hibernate: add trans_pgd public functions
From: Pavel Tatashin
Date: Fri Sep 06 2019 - 12:00:34 EST
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:
> > trans_pgd_create_copy() and trans_pgd_map_page() are going to be
> > the basis for public interface of new subsystem that handles page
> Please don't call this a subsystem. 'sound' and 'mm' are subsystems, this is just some
> shared code.
Sounds good: just could not find a better term to call trans_pgd_*. I
won't fix log commits.
> > tables for cases which are between kernels: kexec, and hibernate.
> Even though you've baked the get_safe_page() calls into trans_pgd_map_page()?
It is getting removed later. Just for a cleaner migration to new
place, get_safe_page() is included for now.
> > diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
> > index 750ecc7f2cbe..2e29d620b56c 100644
> > --- a/arch/arm64/kernel/hibernate.c
> > +++ b/arch/arm64/kernel/hibernate.c
> > @@ -182,39 +182,15 @@ int arch_hibernation_header_restore(void *addr)
> > +int trans_pgd_map_page(pgd_t *trans_pgd, void *page,
> > + unsigned long dst_addr,
> > + pgprot_t pgprot)
> If this thing is going to be exposed, its name should reflect that its creating a set of
> page tables, to map a single page.
> A function called 'map_page' with this prototype should 'obviously' map @page at @dst_addr
> in @trans_pgd using the provided @pgprot... but it doesn't.
> This is what 'create' was doing in the old name, if that wasn't obvious, its because
> naming things is hard!
> | trans_create_single_page_mapping()?
> (might be too verbose)
> I think this bites you in patch 8, where you 'generalise' this.
The new naming makes more sense to me. The old code had function named:
It was doing four things: 1. creating the actual page via provided
allocator, 2. copying content from the provided page to new page, 3
creating a new page table. 4 mapping it to a new page table at
specified destination address
After, I generalize this the function the prototype looks like this:
int trans_pgd_map_page(struct trans_pgd_info *info, pgd_t *trans_pgd,
void *page, unsigned long
dst_addr, pgprot_t pgprot)
The function only does the "4" from the old code: map the specified
page at dst_addr. The trans_pgd is already created. Of course, and
mapping function will have to allocate missing tables in the page
tables when necessary.
> > + return 0;
> > +}
> > +
> > +/*
> > + * Copies length bytes, starting at src_start into an new page,
> > + * perform cache maintentance, then maps it at the specified address low
> Could you fix the spelling of maintenance as git thinks you've moved it?