[RFC KVM 05/27] KVM: x86: Add handler to exit kvm isolation

[Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>]

From: Liran Alon <liran.alon@xxxxxxxxxx>

Interrupt handlers will need this handler to switch from
the KVM address space back to the kernel address space
on their prelog.

Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx>
Signed-off-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
---
 arch/x86/include/asm/irq.h |    1 +
 arch/x86/kernel/irq.c      |   11 +++++++++++
 arch/x86/kvm/isolation.c   |   13 +++++++++++++
 3 files changed, 25 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
index 8f95686..eb32abc 100644
--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -29,6 +29,7 @@ static inline int irq_canonicalize(int irq)
 extern __visible void smp_kvm_posted_intr_ipi(struct pt_regs *regs);
 extern __visible void smp_kvm_posted_intr_wakeup_ipi(struct pt_regs *regs);
 extern __visible void smp_kvm_posted_intr_nested_ipi(struct pt_regs *regs);
+extern void kvm_set_isolation_exit_handler(void (*handler)(void));
 #endif
 
 extern void (*x86_platform_ipi_callback)(void);
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 59b5f2e..e68483b 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -295,6 +295,17 @@ void kvm_set_posted_intr_wakeup_handler(void (*handler)(void))
 }
 EXPORT_SYMBOL_GPL(kvm_set_posted_intr_wakeup_handler);
 
+void (*kvm_isolation_exit_handler)(void) = dummy_handler;
+
+void kvm_set_isolation_exit_handler(void (*handler)(void))
+{
+	if (handler)
+		kvm_isolation_exit_handler = handler;
+	else
+		kvm_isolation_exit_handler = dummy_handler;
+}
+EXPORT_SYMBOL_GPL(kvm_set_isolation_exit_handler);
+
 /*
  * Handler for POSTED_INTERRUPT_VECTOR.
  */
diff --git a/arch/x86/kvm/isolation.c b/arch/x86/kvm/isolation.c
index 35aa659..22ff9c2 100644
--- a/arch/x86/kvm/isolation.c
+++ b/arch/x86/kvm/isolation.c
@@ -5,6 +5,7 @@
  * KVM Address Space Isolation
  */
 
+#include <linux/kvm_host.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/printk.h>
@@ -95,6 +96,16 @@ static void kvm_isolation_uninit_mm(void)
 	free_pages((unsigned long)kvm_pgd, PGD_ALLOCATION_ORDER);
 }
 
+static void kvm_isolation_set_handlers(void)
+{
+	kvm_set_isolation_exit_handler(kvm_isolation_exit);
+}
+
+static void kvm_isolation_clear_handlers(void)
+{
+	kvm_set_isolation_exit_handler(NULL);
+}
+
 int kvm_isolation_init(void)
 {
 	int r;
@@ -106,6 +117,7 @@ int kvm_isolation_init(void)
 	if (r)
 		return r;
 
+	kvm_isolation_set_handlers();
 	pr_info("KVM: x86: Running with isolated address space\n");
 
 	return 0;
@@ -116,6 +128,7 @@ void kvm_isolation_uninit(void)
 	if (!address_space_isolation)
 		return;
 
+	kvm_isolation_clear_handlers();
 	kvm_isolation_uninit_mm();
 	pr_info("KVM: x86: End of isolated address space\n");
 }
-- 
1.7.1