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Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Borislav Petkov , "Edgecombe, Rick P" , Oleg Vasilev , Arthur Petukhovsky , Stefan Radig , Misha Sakhnov References: <22cd0fa8-d14d-4d37-a6a1-5e6827d6182b@intel.com> <2080ec7c-8dc8-4f03-bd96-78ba47e55a97@neon.tech> <7c204a40-532d-4afe-94f9-e685fb9be454@intel.com> Content-Language: en-US From: Em Sharnoff In-Reply-To: <7c204a40-532d-4afe-94f9-e685fb9be454@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/11/25 15:16, Dave Hansen wrote: > On 6/11/25 01:38, Em Sharnoff wrote: >>> Could you please find a way to reduce the number of casts? >> What do you think about changing the return for these functions to just 'int' >> for errors? > Fine with me. No reason to cram errno's into a physical address that's > never used as a physical address. Just realized paddr_last is actually used to set 'max_pfn_mapped'. In init_memory_mapping(): > add_pfn_range_mapped(start >> PAGE_SHIFT, ret >> PAGE_SHIFT); which in turn only uses it to update max_pfn_mapped: > max_pfn_mapped = max(max_pfn_mapped, end_pfn) This was added in cc6150321903 ("x86: account overlapped mappings in max_pfn_mapped"). --- Some other options to reduce the number of casts: 1. Add helpers to do the '(void *)' casting for ERR_PTR, keeping everything else the same. 2. Change the phys_*_init() functions to return int, and directly update max_pfn_mapped from within them. They already call update_page_count(), maybe this is similar? 3. Change the phys_*_init() functions to return int, and calculate the expected paddr_last externally. The third option I think is possible in theory, but probably too complicated and fragile. (at a glance, there's complex emergent logic - but maybe someone familiar with the code could make the case for something simple) Thoughts? Em