3794d5482d
Modern Linux kernels support last POWERPC CPUs so when a kernel boots, in most cases it can find a matching cpu_spec in the kernel's cpu_specs list. However if the kernel is quite old, it may be missing a definition of the actual CPU. To provide an ability for old kernels to work on modern hardware, a Processor Compatibility Mode has been introduced by the PowerISA specification. >From the hardware prospective, it is supported by the Processor Compatibility Register (PCR) which is defined in PowerISA. The register enables one of the compatibility modes (2.05/2.06/2.07). Since PCR is a hypervisor privileged register and cannot be directly accessed from the guest, the mode selection is done via ibm,client-architecture-support (CAS) RTAS call using which the guest specifies what "raw" and "architected" CPU versions it supports. QEMU works out the best match, changes a "cpu-version" property of every CPU and notifies the guest about the change by setting these properties in the buffer passed as a response on a custom H_CAS hypercall. This implements ibm,client-architecture-support parameters parsing (now only for PVRs) and cooks the device tree diff with new values for "cpu-version", "ibm,ppc-interrupt-server#s" and "ibm,ppc-interrupt-server#s" properties. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Signed-off-by: Alexander Graf <agraf@suse.de>
Read the documentation in qemu-doc.html or on http://wiki.qemu-project.org - QEMU team