[PATCH 2/6] Init dirty quota flag and allocate memory for vCPUdqctx.

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

When the VM is created, we initialize the flag to track the start of a
dirty quota migration as false. It is set to true when the dirty quota
migration starts.
When a vCPU is created, we allocate memory for the dirty quota context of
the vCPU. This dirty quota context is mmaped to the userspace when a dirty
quota migration starts.

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/include/uapi/asm/kvm.h       |  1 +
 arch/x86/kvm/Makefile                 |  3 ++-
 include/linux/dirty_quota_migration.h | 16 ++++++++++++++++
 include/uapi/linux/kvm.h              |  9 +++++++++
 virt/kvm/dirty_quota_migration.c      | 14 ++++++++++++++
 virt/kvm/kvm_main.c                   |  8 ++++++++
 6 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 virt/kvm/dirty_quota_migration.c

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 5a776a08f78c..c4270dd9219b 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -13,6 +13,7 @@
 #define KVM_PIO_PAGE_OFFSET 1
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 2
 #define KVM_DIRTY_LOG_PAGE_OFFSET 64
+#define KVM_DIRTY_QUOTA_PAGE_OFFSET 64
 
 #define DE_VECTOR 0
 #define DB_VECTOR 1
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index 75dfd27b6e8a..a26fc0c94a83 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -11,7 +11,8 @@ KVM := ../../../virt/kvm
 
 kvm-y			+= $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o \
 				$(KVM)/eventfd.o $(KVM)/irqchip.o $(KVM)/vfio.o \
-				$(KVM)/dirty_ring.o $(KVM)/binary_stats.o
+				$(KVM)/dirty_ring.o $(KVM)/binary_stats.o \
+				$(KVM)/dirty_quota_migration.o
 kvm-$(CONFIG_KVM_ASYNC_PF)	+= $(KVM)/async_pf.o
 
 kvm-y			+= x86.o emulate.o i8259.o irq.o lapic.o \
diff --git a/include/linux/dirty_quota_migration.h b/include/linux/dirty_quota_migration.h
index 4f4e0d80a04d..8c12fa428436 100644
--- a/include/linux/dirty_quota_migration.h
+++ b/include/linux/dirty_quota_migration.h
@@ -14,4 +14,20 @@ struct vCPUDirtyQuotaContext {
 	u64 dirty_quota;
 };
 
+#if (KVM_DIRTY_QUOTA_PAGE_OFFSET == 0)
+/*
+ * If KVM_DIRTY_QUOTA_PAGE_OFFSET is not defined by the arch, exclude
+ * dirty_quota_migration.o by defining these nop functions for the arch.
+ */
+static inline int kvm_vcpu_dirty_quota_alloc(struct vCPUDirtyQuotaContext **vCPUdqctx)
+{
+	return 0;
+}
+
+#else /* KVM_DIRTY_QUOTA_PAGE_OFFSET == 0 */
+
+int kvm_vcpu_dirty_quota_alloc(struct vCPUDirtyQuotaContext **vCPUdqctx);
+
+#endif /* KVM_DIRTY_QUOTA_PAGE_OFFSET == 0 */
+
 #endif  /* DIRTY_QUOTA_MIGRATION_H */
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 1daa45268de2..647f7e1a04dc 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1905,6 +1905,15 @@ struct kvm_hyperv_eventfd {
 #define KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE    (1 << 0)
 #define KVM_DIRTY_LOG_INITIALLY_SET            (1 << 1)
 
+/*
+ * KVM_DIRTY_QUOTA_PAGE_OFFSET will be defined, and set to the
+ * starting page offset of dirty quota context structure, by the
+ * arch implementing dirty quota migration.
+ */
+#ifndef KVM_DIRTY_QUOTA_PAGE_OFFSET
+#define KVM_DIRTY_QUOTA_PAGE_OFFSET 0
+#endif
+
 /*
  * Arch needs to define the macro after implementing the dirty ring
  * feature.  KVM_DIRTY_LOG_PAGE_OFFSET should be defined as the
diff --git a/virt/kvm/dirty_quota_migration.c b/virt/kvm/dirty_quota_migration.c
new file mode 100644
index 000000000000..262f071aac0c
--- /dev/null
+++ b/virt/kvm/dirty_quota_migration.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include <linux/dirty_quota_migration.h>
+
+int kvm_vcpu_dirty_quota_alloc(struct vCPUDirtyQuotaContext **vCPUdqctx)
+{
+	u64 size = sizeof(struct vCPUDirtyQuotaContext);
+	*vCPUdqctx = vmalloc(size);
+	if (!(*vCPUdqctx))
+		return -ENOMEM;
+	memset((*vCPUdqctx), 0, size);
+	return 0;
+}
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d31724500501..5626ae1b92ce 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -66,6 +66,7 @@
 #include <trace/events/kvm.h>
 
 #include <linux/kvm_dirty_ring.h>
+#include <linux/dirty_quota_migration.h>
 
 /* Worst case buffer size needed for holding an integer. */
 #define ITOA_MAX_LEN 12
@@ -1079,6 +1080,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
 	}
 
 	kvm->max_halt_poll_ns = halt_poll_ns;
+	kvm->dirty_quota_migration_enabled = false;
 
 	r = kvm_arch_init_vm(kvm, type);
 	if (r)
@@ -3638,6 +3640,12 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
 			goto arch_vcpu_destroy;
 	}
 
+	if (KVM_DIRTY_QUOTA_PAGE_OFFSET) {
+		r = kvm_vcpu_dirty_quota_alloc(&vcpu->vCPUdqctx);
+		if (r)
+			goto arch_vcpu_destroy;
+	}
+
 	mutex_lock(&kvm->lock);
 	if (kvm_get_vcpu_by_id(kvm, id)) {
 		r = -EEXIST;
-- 
2.22.3