Commit 5ed73f40 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar

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: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: yu-cheng yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/60662444e13c76f06e23c15c5dcdba31b4ac3d67.1453675014.git.luto@kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 4ecd16ec
......@@ -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);
......@@ -189,9 +193,13 @@ void fpu__save(struct fpu *fpu)
preempt_disable();
if (fpu->fpregs_active) {
if (!copy_fpregs_to_fpstate(fpu))
if (!copy_fpregs_to_fpstate(fpu)) {
if (use_eager_fpu())
copy_kernel_to_fpregs(&fpu->state);
else
fpregs_deactivate(fpu);
}
}
preempt_enable();
}
EXPORT_SYMBOL_GPL(fpu__save);
......@@ -259,6 +267,10 @@ 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);
if (use_eager_fpu())
copy_kernel_to_fpregs(&src_fpu->state);
else
fpregs_deactivate(src_fpu);
}
preempt_enable();
......
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