[RFC PATCH v0 2/5] KVM: PPC: Add support for KVM_REQ_ESN_EXIT

[Bharata B Rao <bharata@linux.ibm.com>]

Add a new KVM exit request KVM_REQ_ESN_EXIT that will be used
to exit to userspace (QEMU) whenever subvention notification
needs to be sent to the guest.

The userspace (QEMU) issues the subvention notification by
injecting an interrupt into the guest.

Signed-off-by: Bharata B Rao <bharata@linux.ibm.com>
---
 arch/powerpc/include/asm/kvm_host.h | 1 +
 arch/powerpc/kvm/book3s_hv.c        | 8 ++++++++
 include/uapi/linux/kvm.h            | 1 +
 3 files changed, 10 insertions(+)

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 9f52f282b1aa..204dc2d91388 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -52,6 +52,7 @@
 #define KVM_REQ_WATCHDOG	KVM_ARCH_REQ(0)
 #define KVM_REQ_EPR_EXIT	KVM_ARCH_REQ(1)
 #define KVM_REQ_PENDING_TIMER	KVM_ARCH_REQ(2)
+#define KVM_REQ_ESN_EXIT	KVM_ARCH_REQ(3)
 
 #include <linux/mmu_notifier.h>
 
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 085fb8ecbf68..47ccd4a2df54 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -2820,6 +2820,14 @@ static void kvmppc_core_vcpu_free_hv(struct kvm_vcpu *vcpu)
 
 static int kvmppc_core_check_requests_hv(struct kvm_vcpu *vcpu)
 {
+	/*
+	 * If subvention interrupt needs to be injected to the guest
+	 * exit to user space.
+	 */
+	if (kvm_check_request(KVM_REQ_ESN_EXIT, vcpu)) {
+		vcpu->run->exit_reason = KVM_EXIT_ESN;
+		return 0;
+	}
 	/* Indicate we want to get back into the guest */
 	return 1;
 }
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index d9e4aabcb31a..47be532ed14b 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -269,6 +269,7 @@ struct kvm_xen_exit {
 #define KVM_EXIT_AP_RESET_HOLD    32
 #define KVM_EXIT_X86_BUS_LOCK     33
 #define KVM_EXIT_XEN              34
+#define KVM_EXIT_ESN		  35
 
 /* For KVM_EXIT_INTERNAL_ERROR */
 /* Emulate instruction failed. */
-- 
2.31.1