xv6

commit 9946b51c909edc0e79529971d104282dcdc77814
parent 6c8e36b21b75ce984120b1eb8a701961bc60dfa2
Author: Brian Swetland <swetland@frotz.net>
Date:   Sat,  4 Jan 2014 16:26:56 -0800

enable SMP in 64bit build

- in startothers() we pass entry32mp instead of entrymp as the
  address that entryother will jump to in 32bit mode
- don't initialize paging in entryother in the 64bit build
  since we defer that until we switch to 64bit mode
- entry32mp is an entrypoint midway through entry64.S that
  shares much of the startup code for the secondary core(s)
  with the bootstrap core

Diffstat:
M
kernel/entry64.S
 | 
18
++++++++++++++++++
M
kernel/entryother.S
 | 
6
++++++
M
kernel/main.c
 | 
9
++++++++-

3 files changed, 32 insertions(+), 1 deletion(-)
diff --git a/kernel/entry64.S b/kernel/entry64.S
@@ -75,6 +75,14 @@ ptbl_loop:
   dec %ecx
   jnz ptbl_loop
 
+# Clear ebx for initial processor boot.
+# When secondary processors boot, they'll call through
+# entry32mp (from entryother), but with a nonzero ebx.
+# We'll reuse these bootstrap pagetables and GDT.
+  xor %ebx, %ebx
+
+.global entry32mp
+entry32mp:
 # CR3 -> 0x1000 (P4ML)
   mov $0x1000, %eax
   mov %eax, %cr3
@@ -133,6 +141,10 @@ entry64high:
   mov %ax, %fs
   mov %ax, %gs
 
+# check to see if we're booting a secondary core
+  test %ebx, %ebx
+  jnz entry64mp
+
 # setup initial stack
   mov $0xFFFFFFFF80010000, %rax
   mov %rax, %rsp
@@ -145,6 +157,12 @@ __deadloop:
 # we should never return here...
   jmp .
 
+entry64mp:
+# obtain kstack from data block before entryother
+  mov $0x7000, %rax
+  mov -16(%rax), %rsp
+  jmp mpenter
+
 .global wrmsr
 wrmsr:
   mov %rdi, %rcx     # arg0 -> msrnum
diff --git a/kernel/entryother.S b/kernel/entryother.S
@@ -49,6 +49,11 @@ start32:
   movw    %ax, %fs
   movw    %ax, %gs
 
+#if X64
+  # defer paging until we switch to 64bit mode
+  # set ebx=1 so shared boot code knows we're booting a secondary core
+  mov     $1, %ebx
+#else
   # Turn on page size extension for 4Mbyte pages
   movl    %cr4, %eax
   orl     $(CR4_PSE), %eax
@@ -60,6 +65,7 @@ start32:
   movl    %cr0, %eax
   orl     $(CR0_PE|CR0_PG|CR0_WP), %eax
   movl    %eax, %cr0
+#endif
 
   # Switch to the stack allocated by startothers()
   movl    (start-4), %esp
diff --git a/kernel/main.c b/kernel/main.c
@@ -44,7 +44,7 @@ main(void)
 }
 
 // Other CPUs jump here from entryother.S.
-static void
+void
 mpenter(void)
 {
   switchkvm(); 
@@ -64,6 +64,7 @@ mpmain(void)
 }
 
 pde_t entrypgdir[];  // For entry.S
+void entry32mp(void);
 
 // Start the non-boot (AP) processors.
 static void
@@ -88,9 +89,15 @@ startothers(void)
     // pgdir to use. We cannot use kpgdir yet, because the AP processor
     // is running in low  memory, so we use entrypgdir for the APs too.
     stack = kalloc();
+#if X64
+    *(uint32*)(code-4) = 0x8000; // just enough stack to get us to entry64mp
+    *(uint32*)(code-8) = v2p(entry32mp);
+    *(uint64*)(code-16) = (uint64) (stack + KSTACKSIZE);
+#else
     *(void**)(code-4) = stack + KSTACKSIZE;
     *(void**)(code-8) = mpenter;
     *(int**)(code-12) = (void *) v2p(entrypgdir);
+#endif
 
     lapicstartap(c->id, v2p(code));