From e577a62f0dc5a1b22ac5687204ec720bb4d8a367 Mon Sep 17 00:00:00 2001 From: Frans Kaashoek Date: Fri, 12 Aug 2011 07:31:52 -0400 Subject: [PATCH] Some comments --- main.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/main.c b/main.c index dabca19..8f95559 100644 --- a/main.c +++ b/main.c @@ -82,7 +82,13 @@ bootothers(void) continue; // Tell bootother.S what stack to use, the address of mpboot and pgdir; - stack = boot_alloc(); // We need a stack below 4Mbyte with bootpgdir + // We cannot use kpgdir yet, because the AP processor is running in low + // memory, so we use bootpgdir for the APs too. kalloc can return addresses + // above 4Mbyte (the machine may have much more physical memory than 4Mbyte), which + // aren't mapped by bootpgdir, so we must allocate a stack using boot_alloc(); + // This introduces the constraint that xv6 cannot invoke until after these last boot_alloc + // invocations. + stack = boot_alloc(); *(void**)(code-4) = stack + KSTACKSIZE; *(void**)(code-8) = mpboot; *(int**)(code-12) = (void *) v2p(bootpgdir);