On 25.07.2013, at 15:38, Alexander Graf wrote: > > On 11.07.2013, at 13:49, Paul Mackerras wrote: > >> Unlike the other general-purpose SPRs, SPRG3 can be read by usermode >> code, and is used in recent kernels to store the CPU and NUMA node >> numbers so that they can be read by VDSO functions. Thus we need to >> load the guest's SPRG3 value into the real SPRG3 register when entering >> the guest, and restore the host's value when exiting the guest. We don't >> need to save the guest SPRG3 value when exiting the guest as usermode >> code can't modify SPRG3. > > This loads SPRG3 on every guest exit, which can happen a lot with instruction emulation. Since the kernel doesn't rely on the contents of SPRG3 we only have to care about it when not in KVM code, right? > > So could we move this to kvmppc_core_vcpu_load/put instead? but then again if all the shadow copy code is negligible performance wise, so is this probably. Applied to kvm-ppc-queue. Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
