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Commit14c07ad89f("x86/kvm/mmu: introduce guest_mmu") brought one subtle change: previously, when switching back from L2 to L1, we were resetting MMU hooks (like mmu->get_cr3()) in kvm_init_mmu() called from nested_vmx_load_cr3() and now we do that in nested_ept_uninit_mmu_context() when we re-target vcpu->arch.mmu pointer. The change itself looks logical: if nested_ept_init_mmu_context() changes something than nested_ept_uninit_mmu_context() restores it back. There is, however, one thing: the following call chain: nested_vmx_load_cr3() kvm_mmu_new_cr3() __kvm_mmu_new_cr3() fast_cr3_switch() cached_root_available() now happens with MMU hooks pointing to the new MMU (root MMU in our case) while previously it was happening with the old one. cached_root_available() tries to stash current root but it is incorrect to read current CR3 with mmu->get_cr3(), we need to use old_mmu->get_cr3() which in case we're switching from L2 to L1 is guest_mmu. (BTW, in shadow page tables case this is a non-issue because we don't switch MMU). While we could've tried to guess that we're switching between MMUs and call the right ->get_cr3() from cached_root_available() this seems to be overly complicated. Instead, just stash the corresponding CR3 when setting root_hpa and make cached_root_available() use the stashed value. Fixes:14c07ad89f("x86/kvm/mmu: introduce guest_mmu") Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.