From 16714ee02e321c95872a198515a95723ac778d06 Mon Sep 17 00:00:00 2001
From: Chris Wright <chrisw@sous-sol.org>
Date: Thu, 21 May 2009 17:08:33 -0700
Subject: [PATCH 02/15] Fix kvm_request_irq race

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.  Also move all this to its
own C file to keep from creating per ojbect file private mutexes.

Signed-off-by: Chris Wright <chrisw@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
(cherry picked from commit kvm-kmod: 94fe7506de12dab1a8d6dc563fd5038a0b46f0a9)
Signed-off-by: Chris Wright <chrisw@redhat.com>
Bugzilla: 498071
Message-Id: <1242950913-30143-3-git-send-email-chrisw@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
RH-Upstream-status: applied
Obsoletes: <20090505180853.GI9877@x200.localdomain>
Acked-by: Juan Quintela <quintela@redhat.com>
Acked-by: Don Dutile <ddutile@redhat.com>
Acked-by: Glauber Costa <glommer@redhat.com>
---
 kernel/external-module-compat-comm.h |   30 ++--------------------
 kernel/ia64/Kbuild                   |    3 +-
 kernel/request-irq-compat.c          |   44 ++++++++++++++++++++++++++++++++++
 kernel/x86/Kbuild                    |    2 +-
 4 files changed, 50 insertions(+), 29 deletions(-)
 create mode 100644 kernel/request-irq-compat.c

diff --git a/kernel/external-module-compat-comm.h b/kernel/external-module-compat-comm.h
index 29db92b..1c986d4 100644
--- a/kernel/external-module-compat-comm.h
+++ b/kernel/external-module-compat-comm.h
@@ -647,33 +647,9 @@ static inline int pci_reset_function(struct pci_dev *dev)
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19)
 
 typedef irqreturn_t (*kvm_irq_handler_t)(int, void *);
-static kvm_irq_handler_t kvm_irq_handlers[NR_IRQS];
-
-static irqreturn_t kvm_irq_thunk(int irq, void *dev_id, struct pt_regs *regs)
-{
-	kvm_irq_handler_t handler = kvm_irq_handlers[irq];
-	return handler(irq, dev_id);
-}
-
-static inline int kvm_request_irq(unsigned int a, kvm_irq_handler_t handler,
-				  unsigned long c, const char *d, void *e)
-{
-	int rc;
-	kvm_irq_handler_t old = kvm_irq_handlers[a];
-	if (old)
-		return -EBUSY;
-	kvm_irq_handlers[a] = handler;
-	rc = request_irq(a, kvm_irq_thunk, c, d, e);
-	if (rc)
-		kvm_irq_handlers[a] = NULL;
-	return rc;
-}
-
-static inline void kvm_free_irq(unsigned int irq, void *dev_id)
-{
-	free_irq(irq, dev_id);
-	kvm_irq_handlers[irq] = NULL;
-}
+int kvm_request_irq(unsigned int a, kvm_irq_handler_t handler, unsigned long c,
+		    const char *d, void *e);
+void kvm_free_irq(unsigned int irq, void *dev_id);
 
 #else
 
diff --git a/kernel/ia64/Kbuild b/kernel/ia64/Kbuild
index 5bc6098..e2c8acc 100644
--- a/kernel/ia64/Kbuild
+++ b/kernel/ia64/Kbuild
@@ -1,7 +1,8 @@
 obj-m := kvm.o kvm-intel.o
 
 kvm-objs := kvm_main.o ioapic.o coalesced_mmio.o kvm-ia64.o kvm_fw.o \
-	irq_comm.o ../anon_inodes.o ../external-module-compat.o
+	irq_comm.o ../anon_inodes.o ../external-module-compat.o \
+	../request-irq-compat.o
 
 ifeq ($(CONFIG_IOMMU_API),y)
 kvm-objs += iommu.o
diff --git a/kernel/request-irq-compat.c b/kernel/request-irq-compat.c
new file mode 100644
index 0000000..51193cb
--- /dev/null
+++ b/kernel/request-irq-compat.c
@@ -0,0 +1,44 @@
+/*
+ * compat for request_irq
+ */
+
+#include <linux/interrupt.h>
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19)
+
+static kvm_irq_handler_t kvm_irq_handlers[NR_IRQS];
+static DEFINE_MUTEX(kvm_irq_handlers_mutex);
+
+static irqreturn_t kvm_irq_thunk(int irq, void *dev_id, struct pt_regs *regs)
+{
+	kvm_irq_handler_t handler = kvm_irq_handlers[irq];
+	return handler(irq, dev_id);
+}
+
+int kvm_request_irq(unsigned int a, kvm_irq_handler_t handler,
+		    unsigned long c, const char *d, void *e)
+{
+	int rc = -EBUSY;
+	kvm_irq_handler_t old;
+
+	mutex_lock(&kvm_irq_handlers_mutex);
+	old = kvm_irq_handlers[a];
+	if (old)
+		goto out;
+	kvm_irq_handlers[a] = handler;
+	rc = request_irq(a, kvm_irq_thunk, c, d, e);
+	if (rc)
+		kvm_irq_handlers[a] = NULL;
+out:
+	mutex_unlock(&kvm_irq_handlers_mutex);
+	return rc;
+}
+
+void kvm_free_irq(unsigned int irq, void *dev_id)
+{
+	mutex_lock(&kvm_irq_handlers_mutex);
+	free_irq(irq, dev_id);
+	kvm_irq_handlers[irq] = NULL;
+	mutex_unlock(&kvm_irq_handlers_mutex);
+}
+
+#endif
diff --git a/kernel/x86/Kbuild b/kernel/x86/Kbuild
index 4ef1168..2457704 100644
--- a/kernel/x86/Kbuild
+++ b/kernel/x86/Kbuild
@@ -5,7 +5,7 @@ include $(obj)/../config.kbuild
 obj-m := kvm.o kvm-intel.o kvm-amd.o
 kvm-objs := kvm_main.o x86.o mmu.o x86_emulate.o ../anon_inodes.o irq.o i8259.o \
 	 lapic.o ioapic.o preempt.o i8254.o coalesced_mmio.o irq_comm.o \
-	 ../external-module-compat.o
+	 ../external-module-compat.o ../request-irq-compat.o
 ifeq ($(EXT_CONFIG_KVM_TRACE),y)
 kvm-objs += kvm_trace.o
 endif
-- 
1.6.3.rc4.29.g8146