On 06.04.22 01:43, Kirill A. Shutemov wrote: > UEFI Specification version 2.9 introduces the concept of memory > acceptance. Some Virtual Machine platforms, such as Intel TDX or AMD > SEV-SNP, requiring memory to be accepted before it can be used by the > guest. Accepting happens via a protocol specific for the Virtual Machine > platform. > > Accepting memory is costly and it makes VMM allocate memory for the > accepted guest physical address range. It's better to postpone memory > acceptance until memory is needed. It lowers boot time and reduces > memory overhead. > > Support of such memory requires a few changes in core-mm code: > > - memblock has to accept memory on allocation; > > - page allocator has to accept memory on the first allocation of the > page; > > Memblock change is trivial. > > The page allocator is modified to accept pages on the first allocation. > PageUnaccepted() is used to indicate that the page requires acceptance. > > Kernel only needs to accept memory once after boot, so during the boot > and warm up phase there will be a lot of memory acceptance. After things > are settled down the only price of the feature if couple of checks for > PageUnaccepted() in allocate and free paths. The check refers a hot > variable (that also encodes PageBuddy()), so it is cheap and not visible > on profiles. > > Architecture has to provide two helpers if it wants to support > unaccepted memory: > > - accept_memory() makes a range of physical addresses accepted. > > - memory_is_unaccepted() checks anything within the range of physical > addresses requires acceptance. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Acked-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> # memblock Thanks, I skimmed over most parts and nothing obvious jumped at me. Dave has some good suggestions; I'll try giving it a thorough in the near future. -- Thanks, David / dhildenb
