[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Question about MDS mitigation
On 2019/5/16 15:58, Andrew Cooper wrote: > On 16/05/2019 08:56, wencongyang (A) wrote: >> >> On 2019/5/16 15:38, Andrew Cooper wrote: >>> On 16/05/2019 03:46, wencongyang (A) wrote: >>>> Hi all >>>> >>>> Fill buffers, load ports are shared between threads on the same physical >>>> core. >>>> We need to run more than one vm on the same physical core. >>>> Is there any complete mitigation for environments utilizing SMT? >>> No - not really. >>> >>> An approach which was worked on was that of synchronised scheduling, >>> whereby privilege transitions are syncrhonised to ensure that we're >>> never running code from different privilege levels concurrently on >>> adjacent threads. (This is the mitigation described as Group Scheduling >>> in >>> https://software.intel.com/security-software-guidance/insights/deep-dive-intel-analysis-microarchitectural-data-sampling >>> ) >> synchronised scheduling is not a complete mitigation. Guest A and Guest B >> run on the same physical core, and the privilege level is the same. So >> Guest A can infer data from Guest B. Guest A cannot infer data from >> hypervisor >> because they are in different privilege levels. > > This is (one of the reasons) why core scheduling is a prerequisite to > synchronised scheduling. > > With core scheduling active, you will never have guest A and B > concurrently running on adjacent threads of the same core. Another question: There are a CPUID bit(TSX_FORCE_ABORT) and MSR(MSR_TSX_FORCE_ABORT) in xsa297/xsa297-4.7-1.patch. But we do not find them in the patchs of kvm. IIUC, this MSR is not for MDS mitigation. Is this right? Thanks Wen Congyang > > ~Andrew > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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