Messages in this thread | | | Date | Wed, 18 Feb 2015 10:36:49 +0100 | From | Sebastian Andrzej Siewior <> | Subject | Re: [PATCH 2/2] powerpc/kvm: Limit MAX_VCPUS for guests running on RT Linux |
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On 02/18/2015 10:32 AM, Bogdan Purcareata wrote: > Due to the introduction of the raw_spinlock for the KVM openpic, guests with a > high number of VCPUs may induce great latencies on the underlying RT Linux > system (e.g. cyclictest reports latencies of ~15ms for guests with 24 VCPUs). > This can be further aggravated by sending a lot of external interrupts to the > guest. > > A malicious app can abuse this scenario, causing a DoS of the host Linux. > Until the KVM openpic code is refactored to use finer lock granularity, impose > a limitation on the number of VCPUs a guest can have when running on a > PREEMPT_RT_FULL system with KVM_MPIC emulation.
How is this possible? You take the raw lock, write a register, release the raw lock. How can the guest lockup the host? Is this write blocking in guest?
Sebastian
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