On Mon, Jan 08, 2024 at 03:30:21AM +0000, Huang, Kai wrote:
> On Mon, 2024-01-08 at 03:13 +0000, Huang, Kai wrote:
> > On Sat, 2023-12-23 at 02:52 +0300, Kirill A. Shutemov wrote:
> > > The helper complements kernel_ident_mapping_init(): it frees the
> > > identity mapping that was previously allocated. It will be used in the
> > > error path to free a partially allocated mapping or if the mapping is no
> > > longer needed.
> > >
> > > The caller provides a struct x86_mapping_info with the free_pgd_page()
> > > callback hooked up and the pgd_t to free.
> > >
> > > Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
> > > ---
> > > arch/x86/include/asm/init.h | 3 ++
> > > arch/x86/mm/ident_map.c | 73 +++++++++++++++++++++++++++++++++++++
> > > 2 files changed, 76 insertions(+)
> > >
> > > diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h
> > > index cc9ccf61b6bd..14d72727d7ee 100644
> > > --- a/arch/x86/include/asm/init.h
> > > +++ b/arch/x86/include/asm/init.h
> > > @@ -6,6 +6,7 @@
> > >
> > > struct x86_mapping_info {
> > > void *(*alloc_pgt_page)(void *); /* allocate buf for page table */
> > > + void (*free_pgt_page)(void *, void *); /* free buf for page table */
> > > void *context; /* context for alloc_pgt_page */
> > > unsigned long page_flag; /* page flag for PMD or PUD entry */
> > > unsigned long offset; /* ident mapping offset */
> > > @@ -16,4 +17,6 @@ struct x86_mapping_info {
> > > int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t
> > > *pgd_page,
> > > unsigned long pstart, unsigned long pend);
> > >
> > > +void kernel_ident_mapping_free(struct x86_mapping_info *info, pgd_t
> > > *pgd);
> >
> > Maybe range-based free function can provide more flexibility (e.g., you can
> > directly call the free function to cleanup in kernel_ident_mapping_init()
> > internally when something goes wrong), but I guess this is sufficient for
> > current use case (and perhaps the majority use cases).
> >
> > Reviewed-by: Kai Huang <kai.hu...@intel.com>
> >
>
> Another argument of range-based free function is, theoretically you can build
> the identical mapping table using different x86_mapping_info on different
> ranges, thus it makes less sense to use one 'struct x86_mapping_info *info' to
> free the entire page table, albeit in this implementation only the
> 'free_pgt_page()' callback is used.
The interface can be changed if there will be need for such behaviour.
This kind of future-proofing rarely helpful.
--
Kiryl Shutsemau / Kirill A. Shutemov
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