From 86bdf3ebcfe1ded055282536fecce13001874740 Mon Sep 17 00:00:00 2001 From: Gavin Shan Date: Thu, 10 Nov 2022 18:49:10 +0800 Subject: KVM: Support dirty ring in conjunction with bitmap ARM64 needs to dirty memory outside of a VCPU context when VGIC/ITS is enabled. It's conflicting with that ring-based dirty page tracking always requires a running VCPU context. Introduce a new flavor of dirty ring that requires the use of both VCPU dirty rings and a dirty bitmap. The expectation is that for non-VCPU sources of dirty memory (such as the VGIC/ITS on arm64), KVM writes to the dirty bitmap. Userspace should scan the dirty bitmap before migrating the VM to the target. Use an additional capability to advertise this behavior. The newly added capability (KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP) can't be enabled before KVM_CAP_DIRTY_LOG_RING_ACQ_REL on ARM64. In this way, the newly added capability is treated as an extension of KVM_CAP_DIRTY_LOG_RING_ACQ_REL. Suggested-by: Marc Zyngier Suggested-by: Peter Xu Co-developed-by: Oliver Upton Signed-off-by: Oliver Upton Signed-off-by: Gavin Shan Acked-by: Peter Xu Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20221110104914.31280-4-gshan@redhat.com --- Documentation/virt/kvm/devices/arm-vgic-its.rst | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'Documentation/virt/kvm/devices') diff --git a/Documentation/virt/kvm/devices/arm-vgic-its.rst b/Documentation/virt/kvm/devices/arm-vgic-its.rst index d257eddbae29..e053124f77c4 100644 --- a/Documentation/virt/kvm/devices/arm-vgic-its.rst +++ b/Documentation/virt/kvm/devices/arm-vgic-its.rst @@ -52,7 +52,10 @@ KVM_DEV_ARM_VGIC_GRP_CTRL KVM_DEV_ARM_ITS_SAVE_TABLES save the ITS table data into guest RAM, at the location provisioned - by the guest in corresponding registers/table entries. + by the guest in corresponding registers/table entries. Should userspace + require a form of dirty tracking to identify which pages are modified + by the saving process, it should use a bitmap even if using another + mechanism to track the memory dirtied by the vCPUs. The layout of the tables in guest memory defines an ABI. The entries are laid out in little endian format as described in the last paragraph. -- cgit v1.2.3