[PATCH v3 5/5] KVM: arm64: Document HDBSS ioctl

Tian Zheng
2026-02-25T04:04:44Z

A new ioctl (KVM_CAP_ARM_HW_DIRTY_STATE_TRACK) provides a mechanism for
userspace to configure the HDBSS buffer size during live migration,
enabling hardware-assisted dirty page tracking.

Signed-off-by: eillon <yezhenyu2@huawei.com>
Signed-off-by: Tian Zheng <zhengtian10@huawei.com>
---
Documentation/virt/kvm/api.rst | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index fc5736839edd..2b5531d40d02 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8896,6 +8896,22 @@ helpful if user space wants to emulate instructions which are not
This capability can be enabled dynamically even if VCPUs were already
created and are running.

+7.47 KVM_CAP_ARM_HW_DIRTY_STATE_TRACK
+----------------------------
+
+:Architectures: arm64
+:Type: VM
+:Parameters: args[0] is the allocation order determining HDBSS buffer size
+ args[1] is 0 to disable, 1 to enable HDBSS
+:Returns: 0 on success, negative value on failure
+
+Enables hardware-assisted dirty page tracking via the Hardware Dirty State
+Tracking Structure (HDBSS).
+
+When live migration is initiated, userspace can enable this feature by
+setting KVM_CAP_ARM_HW_DIRTY_STATE_TRACK through IOCTL. KVM will allocate
+per-vCPU HDBSS buffers.
+
8. Other capabilities.
======================

--
2.33.0