@@ -466,4 +466,6 @@
#define X86_BUG_SMT_RSB X86_BUG(29) /* CPU is vulnerable to Cross-Thread Return Address Predictions */
#define X86_BUG_GDS X86_BUG(30) /* CPU is affected by Gather Data Sampling */
+/* BUG word 2 */
+#define X86_BUG_DIV0 X86_BUG(1*32 + 1) /* AMD DIV0 speculation bug */
#endif /* _ASM_X86_CPUFEATURES_H */
@@ -800,9 +800,11 @@ extern u16 get_llc_id(unsigned int cpu);
#ifdef CONFIG_CPU_SUP_AMD
extern u32 amd_get_nodes_per_socket(void);
extern u32 amd_get_highest_perf(void);
+extern void amd_clear_divider(void);
#else
static inline u32 amd_get_nodes_per_socket(void) { return 0; }
static inline u32 amd_get_highest_perf(void) { return 0; }
+static inline void amd_clear_divider(void) { }
#endif
#define for_each_possible_hypervisor_cpuid_base(function) \
@@ -75,6 +75,10 @@ static const int amd_zenbleed[] =
AMD_MODEL_RANGE(0x17, 0x60, 0x0, 0x7f, 0xf),
AMD_MODEL_RANGE(0x17, 0xa0, 0x0, 0xaf, 0xf));
+static const int amd_div0[] =
+ AMD_LEGACY_ERRATUM(AMD_MODEL_RANGE(0x17, 0x00, 0x0, 0x2f, 0xf),
+ AMD_MODEL_RANGE(0x17, 0x50, 0x0, 0x5f, 0xf));
+
static bool cpu_has_amd_erratum(struct cpuinfo_x86 *cpu, const int *erratum)
{
int osvw_id = *erratum++;
@@ -1115,6 +1119,11 @@ static void init_amd(struct cpuinfo_x86 *c)
check_null_seg_clears_base(c);
zenbleed_check(c);
+
+ if (cpu_has_amd_erratum(c, amd_div0)) {
+ pr_notice_once("AMD Zen1 DIV0 bug detected. Disable SMT for full protection.\n");
+ setup_force_cpu_bug(X86_BUG_DIV0);
+ }
}
#ifdef CONFIG_X86_32
@@ -1256,3 +1265,13 @@ void amd_check_microcode(void)
{
on_each_cpu(zenbleed_check_cpu, NULL, 1);
}
+
+/*
+ * Issue a DIV 0/1 insn to clear any division data from previous DIV
+ * operations.
+ */
+void noinstr amd_clear_divider(void)
+{
+ asm volatile(ALTERNATIVE("", "div %2\n\t", X86_BUG_DIV0)
+ :: "a" (0), "d" (0), "r" (1));
+}
@@ -206,6 +206,8 @@ DEFINE_IDTENTRY(exc_divide_error)
{
do_error_trap(regs, 0, "divide error", X86_TRAP_DE, SIGFPE,
FPE_INTDIV, error_get_trap_addr(regs));
+
+ amd_clear_divider();
}
DEFINE_IDTENTRY(exc_overflow)