Document KVM_CAP_ARM_HDBSS_BUFFER_SIZE, which lets userspace configure the per-vCPU HDBSS buffer size for hardware-assisted dirty tracking during live migration. The capability applies to dirty-bitmap mode only: it is rejected once the dirty ring is enabled, and enabling the ring after a size was configured resets it to the default. Signed-off-by: Tian Zheng <zhengtian10@huawei.com> --- Documentation/virt/kvm/api.rst | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index e0430cc750c9..3a3a14cae134 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -9056,6 +9056,34 @@ enabled, cmma can't be enabled anymore and pfmfi and the storage key interpretation are disabled. If cmma has already been enabled or the hpage_2g module parameter is not set to 1, -EINVAL is returned. +7.48 KVM_CAP_ARM_HDBSS_BUFFER_SIZE +----------------------------------- + +:Architectures: arm64 +:Target: VM +:Parameters: args[0] is the per-vCPU HDBSS buffer size in bytes +:Returns: 0 on success; -EINVAL if the size is invalid or vCPUs have already + been created; -EBUSY if the buffer size was already configured. + +This capability configures the per-vCPU HDBSS buffer size used for +hardware-assisted dirty tracking during live migration. + +Userspace sets the size in bytes via KVM_ENABLE_CAP. KVM allocates +per-vCPU HDBSS buffers of the requested size. + +KVM_CHECK_EXTENSION returns the maximum supported size (``SZ_2M``) +when queried without a VM, or the configured per-VM size (default +``PAGE_SIZE``) when queried with a VM. + +Constraints: + +- The size must be a power of two in [``PAGE_SIZE``, ``SZ_2M``]. +- Dirty-bitmap mode only: rejected with -EINVAL once the dirty ring + (``KVM_CAP_DIRTY_LOG_RING``) is enabled, and enabling the ring after + a size was set resets it to the default. +- Must be set before any vCPU is created; a second setting is rejected + with -EBUSY. + 8. Other capabilities. ====================== -- 2.43.0