On 11/12/2015 07:18, Han, Huaitong wrote: > On Thu, 2015-12-10 at 18:59 +0000, Andrew Cooper wrote: >> On 07/12/15 09:16, Huaitong Han wrote: >>> + >>> + /* PKRU dom0 is always zero */ >>> + if ( likely(!pte_pkeys) ) >>> + return 0; >> This is not an architectural restriction (as far as I can tell). Xen >> must never make assumptions about how a guest chooses to use a >> feature. > Yes, I will remove the code section. > > On my test machine, writing non-zero value to PKRU domain 0 will lead > to a GP fault, this is also conform to the usage scenario, and I will > ask the intel architect the reason why SDM does not describe.
If this is (or is going to be documented as) an architectural restriction, then the code can stay, although I would adjust the comment to /* Architecturally, pkey 0 is always zero. */ Thinking about it, the restriction does make sense. It equates to "the default behaviour of things before the PKRU feature came along". ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
