Two very simple bugfixes, affecting all supported architectures.

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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull KVM fixes from Paolo Bonzini:
 "Two very simple bugfixes, affecting all supported architectures"

[ Two? There's three commits in here.  Oh well, I guess Paolo didn't
  count the preparatory symbol export ]

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: correct null pid check in kvm_vcpu_yield_to()
  KVM: check for !is_zero_pfn() in kvm_is_mmio_pfn()
  mm: export symbol dependencies of is_zero_pfn()

arch/mips/mm/init.c

@@ -53,6 +53,7 @@
  */
 unsigned long empty_zero_page, zero_page_mask;
 EXPORT_SYMBOL_GPL(empty_zero_page);
+EXPORT_SYMBOL(zero_page_mask);
 
 /*
  * Not static inline because used by IP27 special magic initialization code

arch/s390/mm/init.c

@@ -43,6 +43,7 @@ pgd_t swapper_pg_dir[PTRS_PER_PGD] __attribute__((__aligned__(PAGE_SIZE)));
 
 unsigned long empty_zero_page, zero_page_mask;
 EXPORT_SYMBOL(empty_zero_page);
+EXPORT_SYMBOL(zero_page_mask);
 
 static void __init setup_zero_pages(void)
 {

mm/memory.c

@@ -118,6 +118,8 @@ __setup("norandmaps", disable_randmaps);
 unsigned long zero_pfn __read_mostly;
 unsigned long highest_memmap_pfn __read_mostly;
 
+EXPORT_SYMBOL(zero_pfn);
+
 /*
  * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
  */

virt/kvm/kvm_main.c

@@ -110,7 +110,7 @@ static bool largepages_enabled = true;
 bool kvm_is_mmio_pfn(pfn_t pfn)
 {
 	if (pfn_valid(pfn))
-		return PageReserved(pfn_to_page(pfn));
+		return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn));
 
 	return true;
 }
@@ -1725,7 +1725,7 @@ int kvm_vcpu_yield_to(struct kvm_vcpu *target)
 	rcu_read_lock();
 	pid = rcu_dereference(target->pid);
 	if (pid)
-		task = get_pid_task(target->pid, PIDTYPE_PID);
+		task = get_pid_task(pid, PIDTYPE_PID);
 	rcu_read_unlock();
 	if (!task)
 		return ret;