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Subject[tip:x86/fpu] x86, fpu: make eagerfpu= boot param tri-state
Commit-ID:  e00229819f306b1f86134095347e9187dc346bd1
Gitweb: http://git.kernel.org/tip/e00229819f306b1f86134095347e9187dc346bd1
Author: Suresh Siddha <suresh.b.siddha@intel.com>
AuthorDate: Mon, 10 Sep 2012 10:32:32 -0700
Committer: H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Tue, 18 Sep 2012 15:52:24 -0700

x86, fpu: make eagerfpu= boot param tri-state

Add the "eagerfpu=auto" (that selects the default scheme in
enabling eagerfpu) which can override compiled-in boot parameters
like "eagerfpu=on/off" (that force enable/disable eagerfpu).

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1347300665-6209-5-git-send-email-suresh.b.siddha@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
Documentation/kernel-parameters.txt | 4 +++-
arch/x86/kernel/xsave.c | 17 ++++++++++++-----
2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e8f7faa..46a6a82 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1834,8 +1834,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
enabling legacy floating-point and sse state.

eagerfpu= [X86]
- on enable eager fpu restore (default for xsaveopt)
+ on enable eager fpu restore
off disable eager fpu restore
+ auto selects the default scheme, which automatically
+ enables eagerfpu restore for xsaveopt.

nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
wfi(ARM) instruction doesn't work correctly and not to
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index e99f754..4e89b3d 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -508,13 +508,15 @@ static void __init setup_init_fpu_buf(void)
xsave_state(init_xstate_buf, -1);
}

-static int disable_eagerfpu;
+static enum { AUTO, ENABLE, DISABLE } eagerfpu = AUTO;
static int __init eager_fpu_setup(char *s)
{
if (!strcmp(s, "on"))
- setup_force_cpu_cap(X86_FEATURE_EAGER_FPU);
+ eagerfpu = ENABLE;
else if (!strcmp(s, "off"))
- disable_eagerfpu = 1;
+ eagerfpu = DISABLE;
+ else if (!strcmp(s, "auto"))
+ eagerfpu = AUTO;
return 1;
}
__setup("eagerfpu=", eager_fpu_setup);
@@ -557,8 +559,9 @@ static void __init xstate_enable_boot_cpu(void)
prepare_fx_sw_frame();
setup_init_fpu_buf();

- if (cpu_has_xsaveopt && !disable_eagerfpu)
- setup_force_cpu_cap(X86_FEATURE_EAGER_FPU);
+ /* Auto enable eagerfpu for xsaveopt */
+ if (cpu_has_xsaveopt && eagerfpu != DISABLE)
+ eagerfpu = ENABLE;

pr_info("enabled xstate_bv 0x%llx, cntxt size 0x%x\n",
pcntxt_mask, xstate_size);
@@ -598,6 +601,10 @@ void __cpuinit eager_fpu_init(void)

clear_used_math();
current_thread_info()->status = 0;
+
+ if (eagerfpu == ENABLE)
+ setup_force_cpu_cap(X86_FEATURE_EAGER_FPU);
+
if (!cpu_has_eager_fpu) {
stts();
return;

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