035d1ef265
A bus lock is acquired through either split locked access to writeback (WB) memory or any locked access to non-WB memory. It is typically >1000 cycles slower than an atomic operation within a cache and can also disrupts performance on other cores. Virtual Machines can exploit bus locks to degrade the performance of system. To address this kind of performance DOS attack coming from the VMs, bus lock VM exit is introduced in KVM and it can report the bus locks detected in guest. If enabled in KVM, it would exit to the userspace to let the user enforce throttling policies once bus locks acquired in VMs. The availability of bus lock VM exit can be detected through the KVM_CAP_X86_BUS_LOCK_EXIT. The returned bitmap contains the potential policies supported by KVM. The field KVM_BUS_LOCK_DETECTION_EXIT in bitmap is the only supported strategy at present. It indicates that KVM will exit to userspace to handle the bus locks. This patch adds a ratelimit on the bus locks acquired in guest as a mitigation policy. Introduce a new field "bus_lock_ratelimit" to record the limited speed of bus locks in the target VM. The user can specify it through the "bus-lock-ratelimit" as a machine property. In current implementation, the default value of the speed is 0 per second, which means no restrictions on the bus locks. As for ratelimit on detected bus locks, simply set the ratelimit interval to 1s and restrict the quota of bus lock occurence to the value of "bus_lock_ratelimit". A potential alternative is to introduce the time slice as a property which can help the user achieve more precise control. The detail of bus lock VM exit can be found in spec: https://software.intel.com/content/www/us/en/develop/download/intel-architecture-instruction-set-extensions-programming-reference.html Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com> Message-Id: <20210521043820.29678-1-chenyi.qiang@intel.com> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> |
||
|---|---|---|
| .. | ||
| apic-msidef.h | ||
| apic.h | ||
| apic_internal.h | ||
| ich9.h | ||
| intel_iommu.h | ||
| ioapic.h | ||
| ioapic_internal.h | ||
| microvm.h | ||
| pc.h | ||
| topology.h | ||
| vmport.h | ||
| x86-iommu.h | ||
| x86.h | ||