x86/fpu: Use restore_init_xstate() instead of math_state_restore() on kthread exec

oleg-nesterov · Ingo Molnar · commit 9cb6ce823bbd · 2015-03-23T10:13:58.000+01:00
Change flush_thread() to do user_fpu_begin() and restore_init_xstate() instead of math_state_restore(). Note: "TODO: cleanup this horror" is still valid. We do not need init_fpu() at all, we only need fpu_alloc() and memset(0). But this needs other changes, in particular user_fpu_begin() should set used_math(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Pekka Riikonen <priikone@iki.fi> Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com> Cc: Rik van Riel <riel@redhat.com> Cc: Suresh Siddha <sbsiddha@gmail.com> Link: http://lkml.kernel.org/r/20150311173449.GE5032@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
@@ -143,7 +143,8 @@ void flush_thread(void)
 		/* kthread execs. TODO: cleanup this horror. */
 		if (WARN_ON(init_fpu(current)))
 			force_sig(SIGKILL, current);
-		math_state_restore();
+		user_fpu_begin();
+		restore_init_xstate();
 	}
 }
 

Original file line number	Diff line number	Diff line change
`@@ -143,7 +143,8 @@ void flush_thread(void)`
`143`	`143`	`/* kthread execs. TODO: cleanup this horror. */`
`144`	`144`	`if (WARN_ON(init_fpu(current)))`
`145`	`145`	`force_sig(SIGKILL, current);`
`146`		`- math_state_restore();`
	`146`	`+ user_fpu_begin();`
	`147`	`+ restore_init_xstate();`
`147`	`148`	`}`
`148`	`149`	`}`
`149`	`150`