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On arm64 host, different size of L3 cache causes the failure of migration for me. So how to disable L3 cache on guest machine?

Jason Lee
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There's no way to do that. For migration to work for an AArch64 KVM setup, both machines must be exactly identical, including things like cache size ID registers. If your two machines have different L3 cache sizes then migration between them will not work.

Peter Maydell
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  • So there is no way to limit the L3 cache on the guest as well? The best way seems to be directly limit L3 cache size on host to make them the same – Jason Lee Nov 18 '22 at 02:20
  • You can't change the L3 cache size on the host CPU either, it's a fixed property of the hardware. The two host CPUs you migrate between really must be *exactly identical*, not just "pretty close". What hardware is this? – Peter Maydell Nov 18 '22 at 11:22
  • Overall this restriction is due to a missing feature in KVM in the kernel -- there is no way to create a guest vCPU that has different ID register values than what the host has. And for QEMU migration all the ID register values must match on source and destination. – Peter Maydell Nov 18 '22 at 11:23