[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2 2/4] x86: Introduce MSR_UNHANDLED
On 22.02.2021 22:19, Boris Ostrovsky wrote: > > On 2/22/21 6:08 AM, Roger Pau Monné wrote: >> On Fri, Feb 19, 2021 at 09:56:32AM -0500, Boris Ostrovsky wrote: >>> 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? >> I agree that using the msr_policy seems like the most suitable place >> to convey this information between the toolstack and Xen. I wonder if >> it would be fine to have fields in msr_policy that don't directly >> translate into an MSR value? > > > We have xen_msr_entry_t.flags that we can use when passing policy array back > and forth. Then we can ignore xen_msr_entry_t.idx for that entry (although in > earlier version of this series Jan preferred to use idx and leave flags > alone). Which, just to clarify, was not the least because of the flags field being per-entry, i.e. per MSR, while here we want a global indicator. Jan
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