Commit-ID: 5ed73f40735c68d8a656b46d09b1885d3b8740ae Gitweb: http://git.kernel.org/tip/5ed73f40735c68d8a656b46d09b1885d3b8740ae Author: Andy Lutomirski <[email protected]> AuthorDate: Sun, 24 Jan 2016 14:38:07 -0800 Committer: Ingo Molnar <[email protected]> CommitDate: Tue, 9 Feb 2016 15:42:55 +0100
x86/fpu: Fix FNSAVE usage in eagerfpu mode In eager fpu mode, having deactivated FPU without immediately reloading some other context is illegal. Therefore, to recover from FNSAVE, we can't just deactivate the state -- we need to reload it if we're not actively context switching. We had this wrong in fpu__save() and fpu__copy(). Fix both. __kernel_fpu_begin() was fine -- add a comment. This fixes a warning triggerable with nofxsr eagerfpu=on. Signed-off-by: Andy Lutomirski <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Fenghua Yu <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Quentin Casasnovas <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Sai Praneeth Prakhya <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: yu-cheng yu <[email protected]> Link: http://lkml.kernel.org/r/60662444e13c76f06e23c15c5dcdba31b4ac3d67.1453675014.git.l...@kernel.org Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/kernel/fpu/core.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 08e1e11..7a9244d 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -114,6 +114,10 @@ void __kernel_fpu_begin(void) kernel_fpu_disable(); if (fpu->fpregs_active) { + /* + * Ignore return value -- we don't care if reg state + * is clobbered. + */ copy_fpregs_to_fpstate(fpu); } else { this_cpu_write(fpu_fpregs_owner_ctx, NULL); @@ -189,8 +193,12 @@ void fpu__save(struct fpu *fpu) preempt_disable(); if (fpu->fpregs_active) { - if (!copy_fpregs_to_fpstate(fpu)) - fpregs_deactivate(fpu); + if (!copy_fpregs_to_fpstate(fpu)) { + if (use_eager_fpu()) + copy_kernel_to_fpregs(&fpu->state); + else + fpregs_deactivate(fpu); + } } preempt_enable(); } @@ -259,7 +267,11 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu) preempt_disable(); if (!copy_fpregs_to_fpstate(dst_fpu)) { memcpy(&src_fpu->state, &dst_fpu->state, xstate_size); - fpregs_deactivate(src_fpu); + + if (use_eager_fpu()) + copy_kernel_to_fpregs(&src_fpu->state); + else + fpregs_deactivate(src_fpu); } preempt_enable(); }
