Re: [PATCH] KVM: x86: Clear CR3[63:32] on SMM entry from long mode

[Qiliang Yuan]

+Cc Hyper-V folks and linux-hyperv, since the failure is triggered by
Hyper-V's handling of VMRUN for a nested (L1) hypervisor, i.e. KVM
running on WSL2.

For the Hyper-V side: the VMRUN is rejected when the guest state has
CR0.PG=0, EFER.LMA=0 and CR3[63:32] != 0, a combination that bare-metal
SVM does not reject.  Is that check intentional?  If it is not, a
Hyper-V fix would help older KVM versions as well; either way the patch
avoids creating that state in the first place.

The full patch is here:
https://lore.kernel.org/r/20260928-kvm-smm-cr3-upper-bits-v1-1-138f52dd531e@xxxxxxxxx

Thanks,
Qiliang