[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] XSA-60 - how to get back to a sane state
Jan Beulich wrote: >>>> On 04.12.13 at 13:04, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote: >> Jan Beulich wrote: >>>>>> On 03.12.13 at 15:30, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> >>>>>> wrote: >>>> Jan Beulich wrote: >>>>>>>> On 03.12.13 at 04:06, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> >>>>>>>> wrote: >>>>>> I also vote option 2, but only revert 86d60e85, keeping 62652c00 >>>>>> (wbinvd at vmx_ctxt_switch_to) since it's used to avoid being >>>>>> polluted when vcpu migrate to another cpu. >>>>> >>>>> Please explain this in more detail. Both Andrew and I are >>>>> concerned about this extra, but pretty pointless (without being >>>>> done so too in other cases) wbinvd(). In particular you'd have to >>>>> explain what its counterpart was in the code prior to your four >>>>> patch XSA-60 series. >>>> >>>> The wbinvd at vmx_ctxt_switch_to is for case like >>>> 1. vcpu runs at cpu A, flushing cache at vmx_handle_cd; >>>> 2. then the vcpu may switch out and migrate to cpu B; >>>> 3. historically cpu B may has cacheline polluted; >>>> so when the vcpu is scheduled to cpu B, we need flush cache. >>> >>> But you didn't clarify whether/how this case was taken care of >>> _before_ your XSA-60 patches. >>> >> >> I didn't understand your question. What do you mean by 'before my >> XSA-60 patches'? > > Before your 4 patch series was applied (e.g. consider plain > 4.3.1) - how was the situation taken care of that your change > to vmx_ctxt_switch_to() is intended to deal with? > Before my 4 patches (in fact before the 3rd patch 62652c00), Xen just didn't take care of the case. Notice that wbinvd at vmx_ctxt_switch_to is for a corner case (when uc mode). Thanks, Jinsong _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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