Messages in this thread | | | From | Michael Kelley <> | Subject | RE: [PATCH] hyperv: root partition faults writing to VP ASSIST MSR PAGE | Date | Tue, 20 Jul 2021 16:20:44 +0000 |
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From: Wei Liu <wei.liu@kernel.org> Sent: Tuesday, July 20, 2021 6:35 AM > > On Tue, Jul 20, 2021 at 06:55:56PM +0530, Praveen Kumar wrote: > [...] > > > > > >> + if (hv_root_partition && > > >> + ms_hyperv.features & HV_MSR_APIC_ACCESS_AVAILABLE) { > > > > > > Is HV_MSR_APIC_ACCESS_AVAILABLE a root only flag? Shouldn't non-root > > > kernel check this too? > > > > Yes, you are right. Will update this in v2. thanks. > > Please split adding this check to its own patch. > > Ideally one patch only does one thing. > > Wei. >
I was just looking around in the Hyper-V TLFS, and I didn't see anywhere that the ability to set up a VP Assist page is dependent on HV_MSR_APIC_ACCESS_AVAILABLE. Or did I just miss it?
Maybe the VP Assist page is not useful for the APIC EOI optimization Purposes if !HV_MSR_APIC_ACCESS_AVAILABLE, but the VP Assist page has other uses, such as for nested enlightenments. So I wonder if the VP Assist page setup really should be gated on HV_MSR_APIC_ACCESS_AVAILABLE.
Michael
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