On Mon, Jan 08, 2024 at 01:13:18PM +0000, Huang, Kai wrote: > On Mon, 2024-01-08 at 13:17 +0300, [email protected] wrote: > > 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 <[email protected]> > > > > > --- > > > > > 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 <[email protected]> > > > > > > > > > > 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. > > > > Do you want to just pass the 'free_pgt_page' function pointer to > kernel_ident_mapping_free(), instead of 'struct x86_mapping_info *info'? As > mentioned above conceptually the page table can be built from multiple > x86_mapping_info for multiple ranges.
I don't think we have such cases in kernel. Let's not overcomplicate things. I see value in keeping interface symmetric. We can always change things according to needs. -- Kiryl Shutsemau / Kirill A. Shutemov _______________________________________________ kexec mailing list [email protected] http://lists.infradead.org/mailman/listinfo/kexec
