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Commit 4464e210de9e80e38de59df052fe09ea2ff80b1b upstream. We already have the percpu area for the host cpu state, which points to the VCPU, so there's no need to store the VCPU pointer on the stack on every context switch. We can be a little more clever and just use tpidr_el2 for the percpu offset and load the VCPU pointer from the host context. This has the benefit of being able to retrieve the host context even when our stack is corrupted, and it has a potential performance benefit because we trade a store plus a load for an mrs and a load on a round trip to the guest. This does require us to calculate the percpu offset without including the offset from the kernel mapping of the percpu array to the linear mapping of the array (which is what we store in tpidr_el1), because a PC-relative generated address in EL2 is already giving us the hyp alias of the linear mapping of a kernel address. We do this in __cpu_init_hyp_mode() by using kvm_ksym_ref(). The code that accesses ESR_EL2 was previously using an alternative to use the _EL1 accessor on VHE systems, but this was actually unnecessary as the _EL1 accessor aliases the ESR_EL2 register on VHE, and the _EL2 accessor does the same thing on both systems. Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com> Reviewed-by: Andrew Jones <drjones@redhat.com> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.