diff mbox series

[14/24] x86/pkeys: Don't check if PKRU is zero before writting it

Message ID 20190321202632.16810-15-bigeasy@linutronix.de (mailing list archive)
State New, archived
Headers show
Series [01/24] x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig() | expand

Commit Message

Sebastian Andrzej Siewior March 21, 2019, 8:26 p.m. UTC 
write_pkru() checks if the current value is the same as the expected
value. So instead just checking if the current and new value is zero
(and skip the write in such a case) we can benefit from that.

Remove the zero check of PKRU, write_pkru() provides a similar check.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/mm/pkeys.c | 7 -------
 1 file changed, 7 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index 05bb9a44eb1c3..50f65fc1b9a3f 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -142,13 +142,6 @@  u32 init_pkru_value = PKRU_AD_KEY( 1) | PKRU_AD_KEY( 2) | PKRU_AD_KEY( 3) |
 void copy_init_pkru_to_fpregs(void)
 {
 	u32 init_pkru_value_snapshot = READ_ONCE(init_pkru_value);
-	/*
-	 * Any write to PKRU takes it out of the XSAVE 'init
-	 * state' which increases context switch cost.  Avoid
-	 * writing 0 when PKRU was already 0.
-	 */
-	if (!init_pkru_value_snapshot && !read_pkru())
-		return;
 	/*
 	 * Override the PKRU state that came from 'init_fpstate'
 	 * with the baseline from the process.