On Wed, Jun 01, 2022 at 04:39:16PM +0200, David Hildenbrand wrote: > On 01.06.22 16:35, Kirill A. Shutemov wrote: > > On Wed, Jun 01, 2022 at 11:00:23AM +0200, David Hildenbrand wrote: > >> On 17.05.22 17:34, Kirill A. Shutemov wrote: > >>> Currently allocate_e820() only interested in the size of map and size of > >>> memory descriptor to determine how many e820 entries the kernel needs. > >>> > >>> UEFI Specification version 2.9 introduces a new memory type -- > >>> unaccepted memory. To track unaccepted memory kernel needs to allocate > >>> a bitmap. The size of the bitmap is dependent on the maximum physical > >>> address present in the system. A full memory map is required to find > >>> the maximum address. > >>> > >>> Modify allocate_e820() to get a full memory map. > >> > >> Usually we use max_pfn, if we want to know the maximum pfn that's > >> present in the system (well, IIRC, excluding hotunplug). > >> > >> How exactly will this (different?) maximum from UEFI for the bitmap > >> interact with > >> > >> max_pfn = e820__end_of_ram_pfn(); > >> > >> from e820 in existing code > >> > >> ? > > > > I'm not sure I understand the question. > > Essentially, if the PFN you calculate here for the bitmap size will > essentially match later max_pfn. Yes, generally. But is can decrease if kernel transit memory from TYPE_RAM to TYPE_RESERVE. In any case we will not step out of the allocated bitmap. -- Kirill A. Shutemov
