Is anyone here actively working on fixing problems with SMP support
under PV i386? While doing some other maintenance on the
vm_page_alloc() callers in the source tree, I happened to take a look at
cpu_initialize_context() in mp_machdep.c. This function is involved in
bringing up the 2nd, 3rd, etc. CPUs on an SMP system. I spotted a
couple obvious errors. First, the size parameter given to kmem_*()
functions is expected to be in terms of bytes and not pages. Second, I
believe that PV i386 requires PAE to be used. If so, there are out of
range accesses to the array m[].
Index: i386/xen/mp_machdep.c
===================================================================
--- i386/xen/mp_machdep.c (revision 228561)
+++ i386/xen/mp_machdep.c (working copy)
@@ -810,7 +810,7 @@ cpu_initialize_context(unsigned int cpu)
{
/* vcpu_guest_context_t is too large to allocate on the stack.
* Hence we allocate statically and protect it with a lock */
- vm_page_t m[4];
+ vm_page_t m[NPGPTD + 2];
static vcpu_guest_context_t ctxt;
vm_offset_t boot_stack;
vm_offset_t newPTD;
@@ -831,8 +831,8 @@ cpu_initialize_context(unsigned int cpu)
pmap_zero_page(m[i]);
}
- boot_stack = kmem_alloc_nofault(kernel_map, 1);
- newPTD = kmem_alloc_nofault(kernel_map, NPGPTD);
+ boot_stack = kmem_alloc_nofault(kernel_map, PAGE_SIZE);
+ newPTD = kmem_alloc_nofault(kernel_map, NPGPTD * PAGE_SIZE);
ma[0] = VM_PAGE_TO_MACH(m[0])|PG_V;
#ifdef PAE
@@ -854,7 +854,7 @@ cpu_initialize_context(unsigned int cpu)
nkpt*sizeof(vm_paddr_t));
pmap_qremove(newPTD, 4);
- kmem_free(kernel_map, newPTD, 4);
+ kmem_free(kernel_map, newPTD, 4 * PAGE_SIZE);
/*
* map actual idle stack to boot_stack
*/
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