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Re: [PATCH v2 2/4] x86: Introduce MSR_UNHANDLED
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
- Date: Fri, 19 Feb 2021 09:56:32 -0500
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, iwj@xxxxxxxxxxxxxx, wl@xxxxxxx, anthony.perard@xxxxxxxxxx, jbeulich@xxxxxxxx, andrew.cooper3@xxxxxxxxxx, jun.nakajima@xxxxxxxxx, kevin.tian@xxxxxxxxx
- Delivery-date: Fri, 19 Feb 2021 14:56:51 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 2/18/21 5:51 AM, Roger Pau Monné wrote:
> On Wed, Jan 20, 2021 at 05:49:10PM -0500, Boris Ostrovsky wrote:
>> When toolstack updates MSR policy, this MSR offset (which is the last
>> index in the hypervisor MSR range) is used to indicate hypervisor
>> behavior when guest accesses an MSR which is not explicitly emulated.
> It's kind of weird to use an MSR to store this. I assume this is done
> for migration reasons?
Not really. It just seemed to me that MSR policy is the logical place to do
that. Because it *is* a policy of how to deal with such accesses, isn't it?
> Isn't is possible to convey this data in the xl migration stream
> instead of having to pack it with MSRs?
I haven't looked at this but again --- the feature itself has nothing to do
with migration. The fact that folding it into policy makes migration of this
information "just work" is just a nice side benefit of this implementation.
-boris
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