[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Fwd: [PATCH RFC 3/4] x86/AMD: support further feature masking MSRs
>>> On 07.04.14 at 10:52, <andrew.cooper3@xxxxxxxxxx> wrote: > On 07/04/14 07:54, Jan Beulich wrote: >> Andrew otoh, in his attempt to make the feature masking per-VM, >> will clearly need to take this into consideration, or else he'd be >> risking runtime crashes. > > That is a good point which I had not anticipated. The way my fragments > of per-VM code currently works involve explicitly probing the expected > set of MSRs at boot, disabling if not found. In a case like this, the > fam16 would not get the masks if the microcode started below 0x700010a > but subsequently got patched higher. > > Catching this case at runtime is hard - if the command line option is > given, the BIOS is out of date wrt microcode, dom0 boots and applies new > microcode, it is not generally safe to retroactively apply the boot time > mask to dom0 which has already started running. I don't think we should go that far - applying microcode post (Xen-) boot shouldn't affect past choices. But it of course ought to affect future ones (i.e. for guests yet to be created). Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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