[RFC PATCH v2 02/10] x86: KVMGT: use kvm_page_track_write_tracking_enable

[Maxim Levitsky <mlevitsk@redhat.com>]

This allows to enable the write tracking only when KVMGT is
actually used and doesn't carry any penalty otherwise.

Tested by booting a VM with a kvmgt mdev device.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/Kconfig             | 3 ---
 arch/x86/kvm/mmu/mmu.c           | 2 +-
 drivers/gpu/drm/i915/Kconfig     | 1 -
 drivers/gpu/drm/i915/gvt/kvmgt.c | 5 +++++
 4 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index e3cbd77061364..41341905d3734 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -126,7 +126,4 @@ config KVM_XEN
 
 	  If in doubt, say "N".
 
-config KVM_EXTERNAL_WRITE_TRACKING
-	bool
-
 endif # VIRTUALIZATION
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 2c4edae4b026d..23f895d439cf5 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5727,7 +5727,7 @@ int kvm_mmu_init_vm(struct kvm *kvm)
 	node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
 	kvm_page_track_register_notifier(kvm, node);
 
-	if (IS_ENABLED(CONFIG_KVM_EXTERNAL_WRITE_TRACKING) || !tdp_enabled)
+	if (!tdp_enabled)
 		mmu_enable_write_tracking(kvm);
 
 	return 0;
diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
index 98c5450b8eacc..7d8346f4bae11 100644
--- a/drivers/gpu/drm/i915/Kconfig
+++ b/drivers/gpu/drm/i915/Kconfig
@@ -130,7 +130,6 @@ config DRM_I915_GVT_KVMGT
 	depends on DRM_I915_GVT
 	depends on KVM
 	depends on VFIO_MDEV
-	select KVM_EXTERNAL_WRITE_TRACKING
 	default n
 	help
 	  Choose this option if you want to enable KVMGT support for
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 057ec44901045..4c62ab3ef245d 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -1933,6 +1933,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev)
 	struct intel_vgpu *vgpu;
 	struct kvmgt_vdev *vdev;
 	struct kvm *kvm;
+	int ret;
 
 	vgpu = mdev_get_drvdata(mdev);
 	if (handle_valid(vgpu->handle))
@@ -1948,6 +1949,10 @@ static int kvmgt_guest_init(struct mdev_device *mdev)
 	if (__kvmgt_vgpu_exist(vgpu, kvm))
 		return -EEXIST;
 
+	ret = kvm_page_track_write_tracking_enable(kvm);
+	if (ret)
+		return ret;
+
 	info = vzalloc(sizeof(struct kvmgt_guest_info));
 	if (!info)
 		return -ENOMEM;
-- 
2.26.3