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  1. Jun 29, 2021
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  8. Jun 17, 2021
    • Chenyi Qiang's avatar
      i386: Add ratelimit for bus locks acquired in guest · 035d1ef2
      Chenyi Qiang authored
      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: default avatarChenyi Qiang <chenyi.qiang@intel.com>
      Message-Id: <20210521043820.29678-1-chenyi.qiang@intel.com>
      Signed-off-by: default avatarEduardo Habkost <ehabkost@redhat.com>
      035d1ef2
    • Eduardo Habkost's avatar
      Update Linux headers to 5.13-rc4 · 278f064e
      Eduardo Habkost authored
      
      Signed-off-by: default avatarEduardo Habkost <ehabkost@redhat.com>
      Message-Id: <20210603191541.2862286-1-ehabkost@redhat.com>
      Signed-off-by: default avatarEduardo Habkost <ehabkost@redhat.com>
      278f064e
  9. Jun 16, 2021
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