Commit-ID: 110d7f7513bbb916b8654da9e2973ac5bed929a9 Gitweb: http://git.kernel.org/tip/110d7f7513bbb916b8654da9e2973ac5bed929a9 Author: Oleg Nesterov <o...@redhat.com> AuthorDate: Mon, 19 Jan 2015 19:52:12 +0100 Committer: Borislav Petkov <b...@suse.de> CommitDate: Mon, 23 Feb 2015 15:50:45 +0100
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 <o...@redhat.com> Reviewed-by: Rik van Riel <r...@redhat.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Suresh Siddha <sbsid...@gmail.com> Cc: Andy Lutomirski <l...@amacapital.net> Link: http://lkml.kernel.org/r/20150119185212.gd16...@redhat.com Signed-off-by: Borislav Petkov <b...@suse.de> --- arch/x86/kernel/process.c | 7 +++++++ 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 ce8b103..8348037 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 0de1fae..de9dcf8 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); } /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
