On 17/05/18 14:38, Jan Beulich wrote:
>>>> On 17.05.18 at 15:26, <andrew.coop...@citrix.com> wrote:
>> On 17/05/18 14:20, Jan Beulich wrote:
>>> Just like for HVM the feature set should be used for EBX output, while
>>> EAX should be restricted to the low 16 bits and ECX/EDX should be zero.
>>>
>>> Short of there being white listing in place just like on the HVM side,
>>> also zap leaves 6, 9, and 0x80000007 as well as unknown / reserved ones.
>>>
>>> Signed-off-by: Jan Beulich <jbeul...@suse.com>
>> Do you want this for backporting?
> Not really, at least that wasn't a primary goal.
>
>> The changes below are enforced by recalculate_cpuid_policy() (and in
>> particular, recaluclate_misc()) in the hypervisor for the past few
>> releases, and Sergey is currently in the process of making all of this
>> libxc logic disappear.
> Well, maybe I'm simply confused: Commit d297b56682 ("x86/cpuid: Handling
> of IBRS/IBPB, STIBP and IBRS for guests") introduced similar code into
> xc_cpuid_hvm_policy() without doing the same for xc_cpuid_pv_policy().
> That's pretty recent a commit, and one that has been backported all the
> way through to 4.6. Are you saying that was a pointless change then?No sorry - you're completely correct. Without the PV side, a guest will by default get the same settings as dom0. The reason why my XTF tests doesn't notice this is because libxl uses a separate path, and XenServer uses a yet-different path. The PV side wants to gain a matching clzero hunk. My comment about recalculate_cpuid_policy() applies to the clamping part of the change. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
