Revision 9dba988edb31d013003b7f00e82dd56f01db70c3 authored by Aaron Lewis on 31 May 2019, 14:14:52 UTC, committed by Paolo Bonzini on 19 June 2019, 14:11:54 UTC
When running with /sys/module/kvm_intel/parameters/unrestricted_guest=N, test that a kernel warning does not occur informing us that vcpu->mmio_needed=1. This can happen when KVM_RUN is called after a triple fault. This test was made to detect a bug that was reported by Syzkaller (https://groups.google.com/forum/#!topic/syzkaller/lHfau8E3SOE) and fixed with commit bbeac2830f4de ("KVM: X86: Fix residual mmio emulation request to userspace"). Signed-off-by: Aaron Lewis <aaronlewis@google.com> Reviewed-by: Jim Mattson <jmattson@google.com> Reviewed-by: Peter Shier <pshier@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 parent 61cfcd5
dec_and_lock.c
// SPDX-License-Identifier: GPL-2.0
#include <linux/export.h>
#include <linux/spinlock.h>
#include <linux/atomic.h>
/*
* This is an implementation of the notion of "decrement a
* reference count, and return locked if it decremented to zero".
*
* NOTE NOTE NOTE! This is _not_ equivalent to
*
* if (atomic_dec_and_test(&atomic)) {
* spin_lock(&lock);
* return 1;
* }
* return 0;
*
* because the spin-lock and the decrement must be
* "atomic".
*/
int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
{
/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
if (atomic_add_unless(atomic, -1, 1))
return 0;
/* Otherwise do it the slow way */
spin_lock(lock);
if (atomic_dec_and_test(atomic))
return 1;
spin_unlock(lock);
return 0;
}
EXPORT_SYMBOL(_atomic_dec_and_lock);
int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
unsigned long *flags)
{
/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
if (atomic_add_unless(atomic, -1, 1))
return 0;
/* Otherwise do it the slow way */
spin_lock_irqsave(lock, *flags);
if (atomic_dec_and_test(atomic))
return 1;
spin_unlock_irqrestore(lock, *flags);
return 0;
}
EXPORT_SYMBOL(_atomic_dec_and_lock_irqsave);
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