On Mon, Feb 24, 2025 at 04:36:38PM +0200, Mike Rapoport wrote: >On Mon, Feb 24, 2025 at 07:13:55AM +0000, Wei Yang wrote: >> On Thu, Feb 06, 2025 at 03:27:52PM +0200, Mike Rapoport wrote: >> >From: Alexander Graf <graf@xxxxxxxxxx> >> [...] >> >diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c >> >index 82b96ed9890a..0b81cd70b02a 100644 >> >--- a/arch/x86/kernel/e820.c >> >+++ b/arch/x86/kernel/e820.c >> >@@ -1329,6 +1329,24 @@ void __init e820__memblock_setup(void) >> > memblock_add(entry->addr, entry->size); >> > } >> > >> >+ /* >> >+ * At this point with KHO we only allocate from scratch memory. >> >+ * At the same time, we configure memblock to only allow >> >+ * allocations from memory below ISA_END_ADDRESS which is not >> >+ * a natural scratch region, because Linux ignores memory below >> >+ * ISA_END_ADDRESS at runtime. Beside very few (if any) early >> >+ * allocations, we must allocate real-mode trapoline below >> >+ * ISA_END_ADDRESS. >> >+ * >> >+ * To make sure that we can actually perform allocations during >> >+ * this phase, let's mark memory below ISA_END_ADDRESS as scratch >> >+ * so we can allocate from there in a scratch-only world. >> >+ * >> >+ * After real mode trampoline is allocated, we clear scratch >> >+ * marking from the memory below ISA_END_ADDRESS >> >+ */ >> >+ memblock_mark_kho_scratch(0, ISA_END_ADDRESS); >> >+ >> >> At the beginning of e820__memblock_setup() we call memblock_allow_resize(), >> which means during adding memory region it could double the array. And the >> memory used here is from some region just added. > >There are large KHO scratch areas that will be used for most allocations. >Marking the memory below ISA_END_ADDRESS as KHO scratch is required to >satisfy allocations that explicitly limit the allocation to ISA_END_ADDRESS, >e.g the real time trampoline. > Thanks, I see you point. We would add memory region during kho_populate() and mark it scratch. >> But with KHO, I am afraid it would fail? >> >> > /* Throw away partial pages: */ >> > memblock_trim_memory(PAGE_SIZE); >> > >> >> -- >> Wei Yang >> Help you, Help me > >-- >Sincerely yours, >Mike. -- Wei Yang Help you, Help me
