static enum { AUTO, ENABLE, DISABLE } eagerfpu = AUTO;
/*
+ * Find supported xfeatures based on cpu features and command-line input.
+ * This must be called after fpu__init_parse_early_param() is called and
+ * xfeatures_mask is enumerated.
+ */
+u64 __init fpu__get_supported_xfeatures_mask(void)
+{
+ /* Support all xfeatures known to us */
+ if (eagerfpu != DISABLE)
+ return XCNTXT_MASK;
+
+ /* Warning of xfeatures being disabled for no eagerfpu mode */
+ if (xfeatures_mask & XFEATURE_MASK_EAGER) {
+ pr_err("x86/fpu: eagerfpu switching disabled, disabling the following xstate features: 0x%llx.\n",
+ xfeatures_mask & XFEATURE_MASK_EAGER);
+ }
+
+ /* Return a mask that masks out all features requiring eagerfpu mode */
+ return ~XFEATURE_MASK_EAGER;
+}
+
+/*
+ * Disable features dependent on eagerfpu.
+ */
+static void __init fpu__clear_eager_fpu_features(void)
+{
+ setup_clear_cpu_cap(X86_FEATURE_MPX);
+}
+
+/*
* Pick the FPU context switching strategy:
+ *
+ * When eagerfpu is AUTO or ENABLE, we ensure it is ENABLE if either of
+ * the following is true:
+ *
+ * (1) the cpu has xsaveopt, as it has the optimization and doing eager
+ * FPU switching has a relatively low cost compared to a plain xsave;
+ * (2) the cpu has xsave features (e.g. MPX) that depend on eager FPU
+ * switching. Should the kernel boot with noxsaveopt, we support MPX
+ * with eager FPU switching at a higher cost.
*/
static void __init fpu__init_system_ctx_switch(void)
{
WARN_ON_FPU(current->thread.fpu.fpstate_active);
current_thread_info()->status = 0;
- /* Auto enable eagerfpu for xsaveopt */
if (boot_cpu_has(X86_FEATURE_XSAVEOPT) && eagerfpu != DISABLE)
eagerfpu = ENABLE;
- if (xfeatures_mask & XFEATURE_MASK_EAGER) {
- if (eagerfpu == DISABLE) {
- pr_err("x86/fpu: eagerfpu switching disabled, disabling the following xstate features: 0x%llx.\n",
- xfeatures_mask & XFEATURE_MASK_EAGER);
- xfeatures_mask &= ~XFEATURE_MASK_EAGER;
- } else {
- eagerfpu = ENABLE;
- }
- }
+ if (xfeatures_mask & XFEATURE_MASK_EAGER)
+ eagerfpu = ENABLE;
if (eagerfpu == ENABLE)
setup_force_cpu_cap(X86_FEATURE_EAGER_FPU);
* No need to check "eagerfpu=auto" again, since it is the
* initial default.
*/
- if (cmdline_find_option_bool(boot_command_line, "eagerfpu=off"))
+ if (cmdline_find_option_bool(boot_command_line, "eagerfpu=off")) {
eagerfpu = DISABLE;
- else if (cmdline_find_option_bool(boot_command_line, "eagerfpu=on"))
+ fpu__clear_eager_fpu_features();
+ } else if (cmdline_find_option_bool(boot_command_line, "eagerfpu=on")) {
eagerfpu = ENABLE;
+ }
if (cmdline_find_option_bool(boot_command_line, "no387"))
setup_clear_cpu_cap(X86_FEATURE_FPU);