kvm: Nested KVM MMUs need PAE root too
On AMD processors, in PAE 32bit mode, nested KVM instances don't work. The L0 host get a kernel OOPS, which is related to arch.mmu->pae_root being NULL. The reason for this is that when setting up nested KVM instance, arch.mmu is set to &arch.guest_mmu (while normally, it would be &arch.root_mmu). However, the initialization and allocation of pae_root only creates it in root_mmu. KVM code (ie. in mmu_alloc_shadow_roots) then accesses arch.mmu->pae_root, which is the unallocated arch.guest_mmu->pae_root. This fix just allocates (and frees) pae_root in both guest_mmu and root_mmu (and also lm_root if it was allocated). The allocation is subject to previous restrictions ie. it won't allocate anything on 64-bit and AFAIK not on Intel. Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=203923 Fixes: 14c07ad8 ("x86/kvm/mmu: introduce guest_mmu") Signed-off-by: Jiri Palecek <jpalecek@web.de> Tested-by: Jiri Palecek <jpalecek@web.de> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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