KVM: arm64: Commit pending PC adjustemnts before returning to userspace
commit 26778aaa upstream. KVM currently updates PC (and the corresponding exception state) using a two phase approach: first by setting a set of flags, then by converting these flags into a state update when the vcpu is about to enter the guest. However, this creates a disconnect with userspace if the vcpu thread returns there with any exception/PC flag set. In this case, the exposed context is wrong, as userspace doesn't have access to these flags (they aren't architectural). It also means that these flags are preserved across a reset, which isn't expected. To solve this problem, force an explicit synchronisation of the exception state on vcpu exit to userspace. As an optimisation for nVHE systems, only perform this when there is something pending. Reported-by: Zenghui Yu <yuzenghui@huawei.com> Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com> Reviewed-by: Zenghui Yu <yuzenghui@huawei.com> Tested-by: Zenghui Yu <yuzenghui@huawei.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Cc: stable@vger.kernel.org # 5.11 [yuz: stable-5.12.y backport: allocate a new number (15) for __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc to keep the host_hcall array tightly packed] Signed-off-by: Zenghui Yu <yuzenghui@huawei.com> Reviewed-by: Marc Zyngier <maz@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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