[PATCH 5/6] Exit to userspace when dirty quota is full.

[Shivam Kumar <shivam.kumar1@nutanix.com>]

Whenever dirty quota is full (i.e. dirty counter equals dirty quota),
control is passed to the QEMU side, through a KVM exit with the custom exit
reason KVM_EXIT_DIRTY_QUOTA_FULL, to handle the dirty quota full event.

Co-developed-by: Anurag Madnawat <anurag.madnawat@nutanix.com>
Signed-off-by: Anurag Madnawat <anurag.madnawat@nutanix.com>
Signed-off-by: Shivam Kumar <shivam.kumar1@nutanix.com>
Signed-off-by: Shaju Abraham <shaju.abraham@nutanix.com>
Signed-off-by: Manish Mishra <manish.mishra@nutanix.com>
---
 arch/x86/kvm/x86.c                    | 9 +++++++++
 include/linux/dirty_quota_migration.h | 6 ++++++
 include/uapi/linux/kvm.h              | 1 +
 virt/kvm/dirty_quota_migration.c      | 5 +++++
 4 files changed, 21 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dc7eb5fddfd3..32fc7a6f8b86 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -59,6 +59,7 @@
 #include <linux/mem_encrypt.h>
 #include <linux/entry-kvm.h>
 #include <linux/suspend.h>
+#include <linux/dirty_quota_migration.h>
 
 #include <trace/events/kvm.h>
 
@@ -10028,6 +10029,14 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
 				return r;
 			vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
 		}
+
+		/* check for dirty quota migration exit condition if it is enabled */
+		if (vcpu->kvm->dirty_quota_migration_enabled &&
+				is_dirty_quota_full(vcpu->vCPUdqctx)) {
+			vcpu->run->exit_reason = KVM_EXIT_DIRTY_QUOTA_FULL;
+			r = 0;
+			break;
+		}
 	}
 
 	srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
diff --git a/include/linux/dirty_quota_migration.h b/include/linux/dirty_quota_migration.h
index b6c6f5f896dd..b9b3bedd9682 100644
--- a/include/linux/dirty_quota_migration.h
+++ b/include/linux/dirty_quota_migration.h
@@ -30,11 +30,17 @@ static inline struct page *kvm_dirty_quota_context_get_page(
 	return NULL;
 }
 
+static inline bool is_dirty_quota_full(struct vCPUDirtyQuotaContext *vCPUdqctx)
+{
+	return true;
+}
+
 #else /* KVM_DIRTY_QUOTA_PAGE_OFFSET == 0 */
 
 int kvm_vcpu_dirty_quota_alloc(struct vCPUDirtyQuotaContext **vCPUdqctx);
 struct page *kvm_dirty_quota_context_get_page(
 		struct vCPUDirtyQuotaContext *vCPUdqctx, u32 offset);
+bool is_dirty_quota_full(struct vCPUDirtyQuotaContext *vCPUdqctx);
 
 #endif /* KVM_DIRTY_QUOTA_PAGE_OFFSET == 0 */
 
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index a6785644bf47..6ba39a6015b0 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -270,6 +270,7 @@ struct kvm_xen_exit {
 #define KVM_EXIT_X86_BUS_LOCK     33
 #define KVM_EXIT_XEN              34
 #define KVM_EXIT_RISCV_SBI        35
+#define KVM_EXIT_DIRTY_QUOTA_FULL 36
 
 /* For KVM_EXIT_INTERNAL_ERROR */
 /* Emulate instruction failed. */
diff --git a/virt/kvm/dirty_quota_migration.c b/virt/kvm/dirty_quota_migration.c
index 7e9ace760939..eeef19347af4 100644
--- a/virt/kvm/dirty_quota_migration.c
+++ b/virt/kvm/dirty_quota_migration.c
@@ -18,3 +18,8 @@ struct page *kvm_dirty_quota_context_get_page(
 {
 	return vmalloc_to_page((void *)vCPUdqctx + offset * PAGE_SIZE);
 }
+
+bool is_dirty_quota_full(struct vCPUDirtyQuotaContext *vCPUdqctx)
+{
+	return (vCPUdqctx->dirty_counter >= vCPUdqctx->dirty_quota);
+}
-- 
2.22.3