On Tue, 2022-11-22 at 10:10 +0800, Yan Zhao wrote: > Also make enable_mmio_caching to be a per-VM value? > As if the shadow_mmio_value is 0, mmio_caching needs to be disabled. If I recall correctly, Sean said we can disable TDX guests if mmio_caching is disabled (we also will need to change to allow enable_mmio_caching to still be true when mmio_value is 0). SEV_ES has similar logic: void __init sev_hardware_setup(void) { ... /* * SEV-ES requires MMIO caching as KVM doesn't have access to the guest * instruction stream, i.e. can't emulate in response to a #NPF and * instead relies on #NPF(RSVD) being reflected into the guest as #VC * (the guest can then do a #VMGEXIT to request MMIO emulation). */ if (!enable_mmio_caching) goto out;