summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/fpu
diff options
context:
space:
mode:
authoryu-cheng yu <yu-cheng.yu@intel.com>2016-01-06 23:24:53 +0100
committerIngo Molnar <mingo@kernel.org>2016-01-12 11:51:21 +0100
commita5fe93a549c54838063d2952dd9643b0b18aa67f (patch)
tree21f291bf9c27b7e62182b4ced5be5696f0b5396b /arch/x86/kernel/fpu
parentx86/fpu: Disable XGETBV1 when no XSAVE (diff)
downloadlinux-a5fe93a549c54838063d2952dd9643b0b18aa67f.tar.xz
linux-a5fe93a549c54838063d2952dd9643b0b18aa67f.zip
x86/fpu: Disable MPX when eagerfpu is off
This issue is a fallout from the command-line parsing move. When "eagerfpu=off" is given as a command-line input, the kernel should disable MPX support. The decision for turning off MPX was made in fpu__init_system_ctx_switch(), which is after the selection of the XSAVE format. This patch fixes it by getting that decision done earlier in fpu__init_system_xstate(). Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: yu-cheng yu <yu-cheng.yu@intel.com> Link: http://lkml.kernel.org/r/1452119094-7252-4-git-send-email-yu-cheng.yu@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/fpu')
-rw-r--r--arch/x86/kernel/fpu/init.c56
-rw-r--r--arch/x86/kernel/fpu/xstate.c3
2 files changed, 45 insertions, 14 deletions
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 3a45fcd0b924..f0ab36844a6d 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -274,7 +274,45 @@ static void __init fpu__init_system_xstate_size_legacy(void)
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)
{
@@ -286,19 +324,11 @@ 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);
@@ -316,10 +346,12 @@ static void __init fpu__init_parse_early_param(void)
* 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);
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index d489f277a8a0..d425cda5ae6d 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -633,8 +633,7 @@ void __init fpu__init_system_xstate(void)
BUG();
}
- /* Support only the state known to the OS: */
- xfeatures_mask = xfeatures_mask & XCNTXT_MASK;
+ xfeatures_mask &= fpu__get_supported_xfeatures_mask();
/* Enable xstate instructions to be able to continue with initialization: */
fpu__init_cpu_xstate();