[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 1/2] VMX: fix VMCS race on context-switch paths
>>> On 17.02.17 at 09:40, <sergey.dyasli@xxxxxxxxxx> wrote: > On Thu, 2017-02-16 at 04:15 -0700, Jan Beulich wrote: >> When __context_switch() is being bypassed during original context >> switch handling, the vCPU "owning" the VMCS partially loses control of >> it: It will appear non-running to remote CPUs, and hence their attempt >> to pause the owning vCPU will have no effect on it (as it already >> looks to be paused). At the same time the "owning" CPU will re-enable >> interrupts eventually (the lastest when entering the idle loop) and >> hence becomes subject to IPIs from other CPUs requesting access to the >> VMCS. As a result, when __context_switch() finally gets run, the CPU >> may no longer have the VMCS loaded, and hence any accesses to it would >> fail. Hence we may need to re-load the VMCS in vmx_ctxt_switch_from(). >> >> Similarly, when __context_switch() is being bypassed also on the second >> (switch-in) path, VMCS ownership may have been lost and hence needs >> re-establishing. Since there's no existing hook to put this in, add a >> new one. > > This paragraph now has to be replaced with something about > vmx_do_resume() change. Oh, I had tried to remember to update this, but then forgot (ending up mentioning this only in the v2 info). Thanks for noticing. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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