x86, fpu: decouple non-lazy/eager fpu restore from xsave
Decouple non-lazy/eager fpu restore policy from the existence of the xsave
feature. Introduce a synthetic CPUID flag to represent the eagerfpu
policy. "eagerfpu=on" boot paramter will enable the policy.
Requested-by: H. Peter Anvin <hpa@zytor.com>
Requested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1347300665-6209-2-git-send-email-suresh.b.siddha@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index e7752bd..c0afd2c 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -400,7 +400,7 @@
set_used_math();
}
- if (use_xsave())
+ if (use_eager_fpu())
math_state_restore();
return err;
@@ -450,29 +450,11 @@
*/
static inline void xstate_enable(void)
{
- clts();
set_in_cr4(X86_CR4_OSXSAVE);
xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
}
/*
- * This is same as math_state_restore(). But use_xsave() is not yet
- * patched to use math_state_restore().
- */
-static inline void init_restore_xstate(void)
-{
- init_fpu(current);
- __thread_fpu_begin(current);
- xrstor_state(init_xstate_buf, -1);
-}
-
-static inline void xstate_enable_ap(void)
-{
- xstate_enable();
- init_restore_xstate();
-}
-
-/*
* Record the offsets and sizes of different state managed by the xsave
* memory layout.
*/
@@ -500,17 +482,20 @@
/*
* setup the xstate image representing the init state
*/
-static void __init setup_xstate_init(void)
+static void __init setup_init_fpu_buf(void)
{
- setup_xstate_features();
-
/*
* Setup init_xstate_buf to represent the init state of
* all the features managed by the xsave
*/
init_xstate_buf = alloc_bootmem_align(xstate_size,
__alignof__(struct xsave_struct));
- init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
+ fx_finit(&init_xstate_buf->i387);
+
+ if (!cpu_has_xsave)
+ return;
+
+ setup_xstate_features();
/*
* Init all the features state with header_bv being 0x0
@@ -523,6 +508,17 @@
xsave_state(init_xstate_buf, -1);
}
+static int disable_eagerfpu;
+static int __init eager_fpu_setup(char *s)
+{
+ if (!strcmp(s, "on"))
+ setup_force_cpu_cap(X86_FEATURE_EAGER_FPU);
+ else if (!strcmp(s, "off"))
+ disable_eagerfpu = 1;
+ return 1;
+}
+__setup("eagerfpu=", eager_fpu_setup);
+
/*
* Enable and initialize the xsave feature.
*/
@@ -559,15 +555,10 @@
update_regset_xstate_info(xstate_size, pcntxt_mask);
prepare_fx_sw_frame();
-
- setup_xstate_init();
+ setup_init_fpu_buf();
pr_info("enabled xstate_bv 0x%llx, cntxt size 0x%x\n",
pcntxt_mask, xstate_size);
-
- current->thread.fpu.state =
- alloc_bootmem_align(xstate_size, __alignof__(struct xsave_struct));
- init_restore_xstate();
}
/*
@@ -586,6 +577,42 @@
return;
this_func = next_func;
- next_func = xstate_enable_ap;
+ next_func = xstate_enable;
this_func();
}
+
+static inline void __init eager_fpu_init_bp(void)
+{
+ current->thread.fpu.state =
+ alloc_bootmem_align(xstate_size, __alignof__(struct xsave_struct));
+ if (!init_xstate_buf)
+ setup_init_fpu_buf();
+}
+
+void __cpuinit eager_fpu_init(void)
+{
+ static __refdata void (*boot_func)(void) = eager_fpu_init_bp;
+
+ clear_used_math();
+ current_thread_info()->status = 0;
+ if (!cpu_has_eager_fpu) {
+ stts();
+ return;
+ }
+
+ if (boot_func) {
+ boot_func();
+ boot_func = NULL;
+ }
+
+ /*
+ * This is same as math_state_restore(). But use_xsave() is
+ * not yet patched to use math_state_restore().
+ */
+ init_fpu(current);
+ __thread_fpu_begin(current);
+ if (cpu_has_xsave)
+ xrstor_state(init_xstate_buf, -1);
+ else
+ fxrstor_checking(&init_xstate_buf->i387);
+}