[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 16.02.17 at 13:27, <andrew.cooper3@xxxxxxxxxx> wrote: > On 16/02/17 11:15, 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. >> >> Reported-by: Kevin Mayer <Kevin.Mayer@xxxxxxxx> >> Reported-by: Anshul Makkar <anshul.makkar@xxxxxxxxxx> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> > > Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> > > Although I would certainly prefer if we can get another round of testing > on this series for confidence. Sure, I'd certainly like to stick a Tested-by on it. Plus VMX maintainer feedback will need waiting for anyway. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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