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x86/mm: Get rid of VM_BUG_ON in switch_tlb_irqs_off() 

If we hit the VM_BUG_ON(), we're detecting a genuinely bad situation,
but we're very unlikely to get a useful call trace.

Make it a warning instead.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/3b4e06bbb382ca54a93218407c93925ff5871546.1504847163.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2017-09-07 22:06:57 -07:00 committed by Ingo Molnar
parent 6d8ef53e8b
commit a376e7f99b
1 changed files with 21 additions and 1 deletions
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22
arch/x86/mm/tlb.c
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@ -121,8 +121,28 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
* hypothetical buggy code that directly switches to swapper_pg_dir
* without going through leave_mm() / switch_mm_irqs_off() or that
* does something like write_cr3(read_cr3_pa()).
*
* Only do this check if CONFIG_DEBUG_VM=y because __read_cr3()
* isn't free.
*/
VM_BUG_ON(__read_cr3() != (__sme_pa(real_prev->pgd) | prev_asid));
#ifdef CONFIG_DEBUG_VM
if (WARN_ON_ONCE(__read_cr3() !=
(__sme_pa(real_prev->pgd) | prev_asid))) {
/*
* If we were to BUG here, we'd be very likely to kill
* the system so hard that we don't see the call trace.
* Try to recover instead by ignoring the error and doing
* a global flush to minimize the chance of corruption.
*
* (This is far from being a fully correct recovery.
* Architecturally, the CPU could prefetch something
* back into an incorrect ASID slot and leave it there
* to cause trouble down the road. It's better than
* nothing, though.)
*/
__flush_tlb_all();
}
#endif
if (real_prev == next) {
VM_BUG_ON(this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) !=