On Fri, Sep 06, 2013 at 10:58:16AM +0530, Aneesh Kumar K.V wrote: > Paul Mackerras <paulus@xxxxxxxxx> writes: > > > This enables us to use the Processor Compatibility Register (PCR) on > > POWER7 to put the processor into architecture 2.05 compatibility mode > > when running a guest. In this mode the new instructions and registers > > that were introduced on POWER7 are disabled in user mode. This > > includes all the VSX facilities plus several other instructions such > > as ldbrx, stdbrx, popcntw, popcntd, etc. > > > > To select this mode, we have a new register accessible through the > > set/get_one_reg interface, called KVM_REG_PPC_ARCH_COMPAT. Setting > > this to zero gives the full set of capabilities of the processor. > > Setting it to one of the "logical" PVR values defined in PAPR puts > > the vcpu into the compatibility mode for the corresponding > > architecture level. The supported values are: > > > > 0x0f000002 Architecture 2.05 (POWER6) > > 0x0f000003 Architecture 2.06 (POWER7) > > 0x0f100003 Architecture 2.06+ (POWER7+) > > > > Since the PCR is per-core, the architecture compatibility level and > > the corresponding PCR value are stored in the struct kvmppc_vcore, and > > are therefore shared between all vcpus in a virtual core. > > We already have KVM_SET_SREGS taking pvr as argument. Can't we do > this kvmppc_set_pvr ?. Can you also share the qemu changes ? There I > guess we need to do update the "cpu-version" in the device tree so > that /proc/cpuinfo shows the right information in the guest The discussion on the qemu mailing list pointed out that we aren't really changing the PVR; the guest still sees the real PVR, and what we're doing is setting a mode of the CPU rather than changing it into an older CPU. So, it seemed better to use something separate from the PVR. Also, if we used the pvr setting to convey this information, then apparently under TCG the guest would see the logical PVR value if it read the (apparently) real PVR. Alexey is working on the relevant QEMU patches. Paul. -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
