Diffstat (limited to 'arch/x86/ia32/ia32entry.S')
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index a821b1cd4fa7..72bf2680f819 100644
@@ -427,6 +427,13 @@ sysretl_from_sys_call:
* cs and ss are loaded from MSRs.
* (Note: 32bit->32bit SYSRET is different: since r11
* does not exist, it merely sets eflags.IF=1).
+ * NB: On AMD CPUs with the X86_BUG_SYSRET_SS_ATTRS bug, the ss
+ * descriptor is not reinitialized. This means that we must
+ * avoid SYSRET with SS == NULL, which could happen if we schedule,
+ * exit the kernel, and re-enter using an interrupt vector. (All
+ * interrupt entries on x86_64 set SS to NULL.) We prevent that
+ * from happening by reloading SS in __switch_to.