mirror of https://github.com/xemu-project/xemu.git
e5ca28ecab
Currently during KVM initialization on POWER, kvm_fixup_page_sizes() rewrites a bunch of information in the cpu state to reflect the capabilities of the host MMU and KVM. This overwrites the information that's already there reflecting how the TCG implementation of the MMU will operate. This means that we can get guest-visibly different behaviour between KVM and TCG (and between different KVM implementations). That's bad. It also prevents migration between KVM and TCG. The pseries machine type now has filtering of the pagesizes it allows the guest to use which means it can present a consistent model of the MMU across all accelerators. So, we can now replace kvm_fixup_page_sizes() with kvm_check_mmu() which merely verifies that the expected cpu model can be faithfully handled by KVM, rather than updating the cpu model to match KVM. We call kvm_check_mmu() from the spapr cpu reset code. This is a hack: conceptually it makes more sense where fixup_page_sizes() was - in the KVM cpu init path. However, doing that would require moving the platform's pagesize filtering much earlier, which would require a lot of work making further adjustments. There wouldn't be a lot of concrete point to doing that, since the only KVM implementation which has the awkward MMU restrictions is KVM HV, which can only work with an spapr guest anyway. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Reviewed-by: Cédric Le Goater <clg@kaod.org> |
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