Chris Wright wrote:
Commit "32658734: Fix request_irq() for < 2.6.19" is racy between multiple
guests since ioctl is only serialized per guest.  Add mutex and serialize
kvm_request_irq/kvm_free_irq to avoid race.

Signed-off-by: Chris Wright <[email protected]>
---
 external-module-compat-comm.h |   14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/external-module-compat-comm.h b/external-module-compat-comm.h
index 8cb5440..eaad986 100644
--- a/external-module-compat-comm.h
+++ b/external-module-compat-comm.h
@@ -645,6 +645,7 @@ static inline int pci_reset_function(struct pci_dev *dev)
typedef irqreturn_t (*kvm_irq_handler_t)(int, void *);
 static kvm_irq_handler_t kvm_irq_handlers[NR_IRQS];
+static DEFINE_MUTEX(kvm_irq_handlers_mutex);

Since this mutex is in a header file, it can be instantiated multiple times. It will only serialize callers within a translation unit. Please define it in a C file.

Would be best to move the the code as well.

--
Do not meddle in the internals of kernels, for they are subtle and quick to 
panic.

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