On Wed, 2025-02-05 at 11:20 -0800, Sean Christopherson wrote: > On Wed, Feb 05, 2025, David Woodhouse wrote: > > On Wed, 2025-02-05 at 16:18 +0000, David Woodhouse wrote: > > > > > > > Oh! It doesn't help KVM avoid breaking userspace, but a way for QEMU to avoid a > > > > future collision would be to have QEMU start at 0x40000200 when Hyper-V is enabled, > > > > but then use KVM_GET_MSR_INDEX_LIST to detect a collision with KVM Hyper-V, e.g. > > > > increment the index until an available index is found (with sanity checks and whatnot). > > > > > > Makes sense. I think that's a third separate patch, yes? > > > > To be clear, I think I mean a third patch which further restricts > > kvm_xen_hvm_config() to disallow indices for which > > kvm_is_advertised_msr() returns true? > > > > We could roll that into your original patch instead, if you prefer. > > Nah, I like the idea of separate patch. Helpfully, kvm_is_advertised_msr() doesn't actually return true for MSR_IA32_XSS. Is that a bug? And kvm_vcpu_reset() attempts to set MSR_IA32_XSS even if the guest doesn't have X86_FEATURE_XSAVES. Is that a bug?
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