Use PFR0 to identify need for mitigation of CVE-2017-5715
If the CSV2 field reads as 1 then branch targets trained in one
context cannot affect speculative execution in a different context.
In that case skip the workaround on Cortex A72 and A73.
Change-Id: Ide24fb6efc77c548e4296295adc38dca87d042ee
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
diff --git a/include/lib/cpus/aarch64/cpu_macros.S b/include/lib/cpus/aarch64/cpu_macros.S
index ccf5306..6c3a5b9 100644
--- a/include/lib/cpus/aarch64/cpu_macros.S
+++ b/include/lib/cpus/aarch64/cpu_macros.S
@@ -229,3 +229,18 @@
#endif
#endif /* __CPU_MACROS_S__ */
+
+ /*
+ * This macro is used on some CPUs to detect if they are vulnerable
+ * to CVE-2017-5715.
+ */
+ .macro cpu_check_csv2 _reg _label
+ mrs \_reg, id_aa64pfr0_el1
+ ubfx \_reg, \_reg, #ID_AA64PFR0_CSV2_SHIFT, #ID_AA64PFR0_CSV2_LENGTH
+ /*
+ * If the field equals to 1 then branch targets trained in one
+ * context cannot affect speculative execution in a different context.
+ */
+ cmp \_reg, #1
+ beq \_label
+ .endm