diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2015-01-19 19:52:12 +0100 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2015-02-23 15:50:45 +0100 |
| commit | 110d7f7513bbb916b8654da9e2973ac5bed929a9 (patch) | |
| tree | 923e255abef680d1354c3e18df2044f19d6dbcbb | |
| parent | 4b2e762e2e53c721458a83d547b222178bb72a34 (diff) | |
| download | linux-110d7f7513bbb916b8654da9e2973ac5bed929a9.tar.bz2 | |
x86/fpu: Don't abuse FPU in kernel threads if use_eager_fpu()
AFAICS, there is no reason why kernel threads should have FPU context
even if use_eager_fpu() == T. Now that interrupted_kernel_fpu_idle()
does not check __thread_has_fpu() in the use_eager_fpu() case, we
can remove the init_fpu() code from eager_fpu_init() and change
flush_thread() called by do_execve() to initialize FPU.
Note: of course, the change in flush_thread() is horrible and must be
cleanuped. We need the new helper, and flush_thread() should return the
error if init_fpu() fails.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Suresh Siddha <sbsiddha@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/20150119185212.GD16427@redhat.com
Signed-off-by: Borislav Petkov <bp@suse.de>
| -rw-r--r-- | arch/x86/kernel/process.c | 7 | ||||
| -rw-r--r-- | arch/x86/kernel/xsave.c | 13 |
2 files changed, 8 insertions, 12 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index ce8b10351e28..83480373a642 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -130,6 +130,7 @@ void flush_thread(void) flush_ptrace_hw_breakpoint(tsk); memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array)); + drop_init_fpu(tsk); /* * Free the FPU state for non xsave platforms. They get reallocated @@ -137,6 +138,12 @@ void flush_thread(void) */ if (!use_eager_fpu()) free_thread_xstate(tsk); + else if (!used_math()) { + /* kthread execs. TODO: cleanup this horror. */ + if (WARN_ON(init_fpu(current))) + force_sig(SIGKILL, current); + math_state_restore(); + } } static void hard_disable_TSC(void) diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c index 0de1fae2bdf0..de9dcf89a302 100644 --- a/arch/x86/kernel/xsave.c +++ b/arch/x86/kernel/xsave.c @@ -688,7 +688,7 @@ void eager_fpu_init(void) { static __refdata void (*boot_func)(void) = eager_fpu_init_bp; - clear_used_math(); + WARN_ON(used_math()); current_thread_info()->status = 0; if (eagerfpu == ENABLE) @@ -703,17 +703,6 @@ void eager_fpu_init(void) 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); } /* |