1 files changed, 10 insertions, 1 deletions

diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 166af2a8e865..04478103df37 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -53,7 +53,16 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
                 /* Stop flush ipis for the previous mm */
                 cpumask_clear_cpu(cpu, mm_cpumask(prev));
 
-                /* Load the LDT, if the LDT is different: */
+                /*
+                 * Load the LDT, if the LDT is different.
+                 *
+                 * It's possible leave_mm(prev) has been called.  If so,
+                 * then prev->context.ldt could be out of sync with the
+                 * LDT descriptor or the LDT register.  This can only happen
+                 * if prev->context.ldt is non-null, since we never free
+                 * an LDT.  But LDTs can't be shared across mms, so
+                 * prev->context.ldt won't be equal to next->context.ldt.
+                 */
                 if (unlikely(prev->context.ldt != next->context.ldt))
                         load_LDT_nolock(&next->context);
         }