Re: [BUG] KVM: x86: Hyper-V VP-assist page reuses the KVM PV-EOI gfn_to_hva_cache, so enabling both WARNs and fails KVM_RUN

[Amirmohammad Eftekhar <amirmohammad.eftekhar@cispa.de>]

Agreed, the stopgap looks right. Gating kvm_hv_get_assist_page() on
vcpu->arch.pv_eoi.data.len >= sizeof(struct hv_vp_assist_page) avoids the WARN
cleanly: when the shared cache is set up for PV EOI's single byte, the
VP-assist read is treated as inaccessible, with no need to untangle the shared
pv_eoi.data storage. And I agree making both features work at different GPAs
isn't worth chasing.

Would you like me to send this as a formal patch, with your Suggested-by,
tested against the reproducer (both features enabled at different GPAs,
confirming the WARN is gone and a well-formed VP-assist still reads back)?

Thanks,
Amirmohammad