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Open Source and information security mailing list archives
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Date: Wed, 18 Feb 2015 10:36:49 +0100 From: Sebastian Andrzej Siewior <bigeasy@...utronix.de> To: Bogdan Purcareata <bogdan.purcareata@...escale.com>, linuxppc-dev@...ts.ozlabs.org, linux-rt-users@...r.kernel.org, agraf@...e.de, pbonzini@...hat.com CC: linux-kernel@...r.kernel.org, scottwood@...escale.com, mihai.caraman@...escale.com Subject: Re: [PATCH 2/2] powerpc/kvm: Limit MAX_VCPUS for guests running on RT Linux 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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