Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Thomas Gleixner:
 "This set of updates contains:

   - Another bugfix for the pathologic vm86 machinery.  Clear
     thread.vm86 on fork to prevent corrupting the parent state.  This
     comes along with an update to the vm86 selftest case

   - Fix another corner case in the ioapic setup code which causes a
     boot crash on some oddball systems

   - Fix the fallout from the dma allocation consolidation work, which
     leads to a NULL pointer dereference when the allocation code is
     called with a NULL device"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/vm86: Set thread.vm86 to NULL on fork/clone
  selftests/x86: Add a fork() to entry_from_vm86 to catch fork bugs
  x86/ioapic: Prevent NULL pointer dereference in setup_ioapic_dest()
  x86/dma-mapping: Fix arch_dma_alloc_attrs() oops with NULL dev

arch/x86/kernel/apic/io_apic.c

@@ -2547,6 +2547,8 @@ void __init setup_ioapic_dest(void)
 			mask = apic->target_cpus();
 
 		chip = irq_data_get_irq_chip(idata);
+		/* Might be lapic_chip for irq 0 */
+		if (chip->irq_set_affinity)
 			chip->irq_set_affinity(idata, mask, false);
 	}
 }

arch/x86/kernel/pci-dma.c

@@ -131,11 +131,12 @@ void dma_generic_free_coherent(struct device *dev, size_t size, void *vaddr,
 
 bool arch_dma_alloc_attrs(struct device **dev, gfp_t *gfp)
 {
+	if (!*dev)
+		*dev = &x86_dma_fallback_dev;
+
 	*gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
 	*gfp = dma_alloc_coherent_gfp_flags(*dev, *gfp);
 
-	if (!*dev)
-		*dev = &x86_dma_fallback_dev;
 	if (!is_device_dma_capable(*dev))
 		return false;
 	return true;

arch/x86/kernel/process.c

@@ -84,6 +84,9 @@ EXPORT_SYMBOL_GPL(idle_notifier_unregister);
 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 {
 	memcpy(dst, src, arch_task_struct_size);
+#ifdef CONFIG_VM86
+	dst->thread.vm86 = NULL;
+#endif
 
 	return fpu__copy(&dst->thread.fpu, &src->thread.fpu);
 }

tools/testing/selftests/x86/entry_from_vm86.c

@@ -230,5 +230,9 @@ int main(void)
 	}
 	clearhandler(SIGSEGV);
 
+	/* Make sure nothing explodes if we fork. */
+	if (fork() > 0)
+		return 0;
+
 	return (nerrs == 0 ? 0 : 1);
 }