On 05/11/18 16:25, Ian Jackson wrote:
> Andrew Cooper writes ("[Xen-devel] MSR load lists on Harpertown"):
>> I realise this is an old CPU, but I've I've encountered a weird failure
>> on it.
> ...
>> However, given this behaviour, I can't think of any way to context
>> switch NX properly, and leave 64bit guests in a working state.
>>
>> Do you have any suggestions?
> ISTM that Xen should run on these old CPUs and also that it should
> work, ideally, even if the microcode is buggy.
>
> So presumaly the right answer is to simply disable NX for the guest
> completely ?As you've observed, when SCE doesn't work, everything is fully hosed. However, disabling NX on that CPU won't fix the problem, because the problem appears to be using the MSR load list. Without a microcode fix (if indeed this is a microcode issue, but given how much of vmentry is, I'd be surprised if it is something else), the only fix I can see is to effectively revert the change to use MSR load lists. However, I really don't want to do this unilaterally, because it will break NX handling on all Intel hardware, and reintroduce a wart into the context switch code which I thought I'd excised properly. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
