[PATCH 111/208] x86/fpu: Do CLTS fpu__init_system()

[Ingo Molnar]

mxcsr_feature_mask_init() depends on TS being cleared, as it executes
an FXSAVE instruction.

After later changes we will move the TS setup into fpu__init_cpu(),
which will interact with this - so clear the TS flag explicitly.

Reviewed-by: Borislav Petkov <bp@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/fpu/init.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 2752b4bae854..567e7e6cdc6b 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -214,6 +214,13 @@ void fpu__init_system(void)
 	fpu__init_cpu();
 
 	/*
+	 * But don't leave CR0::TS set yet, as some of the FPU setup methods depend
+	 * on being able to execute FPU instructions that will fault on a set TS,
+	 * such as the FXSAVE in mxcsr_feature_mask_init().
+	 */
+	clts();
+
+	/*
 	 * Set up the legacy init FPU context. (xstate init might overwrite this
 	 * with a more modern format, if the CPU supports it.)
 	 */
-- 
2.1.0

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