On 03/07/2019 07:30, Juergen Gross wrote: > On 02.07.19 18:09, Andrew Cooper wrote: >> On 28/05/2019 11:32, Juergen Gross wrote: >>> Instead of dynamically decide whether the previous vcpu was using full >> >> "deciding" >> >>> or default GDT just add a percpu variable for that purpose. This at >> >> "was using a full or default GDT, just add" >> >>> once removes the need for testing vcpu_ids to differ twice. >>> >>> Cache the need_full_gdt(nd) value in a local variable. >> >> What's the point of doing this? I know the logic is rather complicated >> in __context_switch(), but at least it is visually consistent. After >> this change, it is asymmetric and harder to follow. > > This is a hot path. need_full_gdt() needs two compares, of which one is > using evaluate_nospec().
Urgh. So evalute_nospec() is already broken here because need_full_gdt() isn't always_inline, but surely this isn't the only example impacted in __context_switch()? The choice of 'gdt' is similarly impacted by the looks of things. I'd recommend not worrying about evalute_nospec() for now. There are several fundamental problems atm, and Xen 4.13 cannot ship with it in this state. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
