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x86/fpu: Handle #NM without FPU emulation as an error

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Don't use CR0.TS.  Make it an error rather than making nonsensical
changes to the FPU state.

(The cond_local_irq_enable() appears to have been pointless, too.)

Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Quentin Casasnovas <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Rusty Russell <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: kvm list <[email protected]>
Link: http://lkml.kernel.org/r/f1ee6bf73ed1025fccaab321ba43d0594245f927.1477951965.git.luto@kernel.org
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Andy Lutomirski authored and Ingo Molnar committed 2016-11-01 07:47:54 +01:00
1 parent cd95ea81f2
commit bef8b6da95
1 file changed
+16 -4
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arch/x86/kernel/traps.c
+16 -4
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@@ -853,6 +853,8 @@ do_spurious_interrupt_bug(struct pt_regs *regs, long error_code)
dotraplinkage void
do_device_not_available(struct pt_regs *regs, long error_code)
{
unsigned long cr0;
RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
#ifdef CONFIG_MATH_EMULATION
@@ -866,10 +868,20 @@ do_device_not_available(struct pt_regs *regs, long error_code)
return;
}
#endif
fpu__restore(&current->thread.fpu); /* interrupts still off */
#ifdef CONFIG_X86_32
cond_local_irq_enable(regs);
#endif
/* This should not happen. */
cr0 = read_cr0();
if (WARN(cr0 & X86_CR0_TS, "CR0.TS was set")) {
/* Try to fix it up and carry on. */
write_cr0(cr0 & ~X86_CR0_TS);
} else {
/*
* Something terrible happened, and we're better off trying
* to kill the task than getting stuck in a never-ending
* loop of #NM faults.
*/
die("unexpected #NM exception", regs, error_code);
}
}
NOKPROBE_SYMBOL(do_device_not_available);