On 27 February 2014 10:35, Pranavkumar Sawargaonkar <pranavkumar@xxxxxxxxxx> wrote: > Hi Peter, > > On 27 February 2014 15:23, Peter Maydell <peter.maydell@xxxxxxxxxx> wrote: >> On 27 February 2014 06:51, Pranavkumar Sawargaonkar >> <pranavkumar@xxxxxxxxxx> wrote: >>> We need to "Feed the kernel back its initial register state" using KVM >>> ioctls for KVM ARM64 (just like KVM ARM). This means we need to save >>> the "initial register state" in kvm_arch_init_vcpu() which is not the >>> case for KVM ARM64 right now. In simpler work, we are depended upon >>> VCPU register init/save/restore for implementing kvm_arch_reset_vcpu(). >>> >>> This patch adds a hacky implementation of kvm_arch_reset_vcpu() which >>> only works for "mach-virt". As-per this hacky implemenation, we re-init >>> the VCPU using kvm_arch_init_vcpu() so that all registers of VCPU are >>> set to their reset values by in-kernel KVM code. >> >> Re-initing the VCPU is actually the right way to do this -- it is feeding >> all the register state back to KVM that is the hack. (One day I may >> fix 32 bit ARM to re-init the VCPU). >> > > Ok, I mentioned this a hack since it is different from arm32 way. > I will update patch comment and description accordingly. > >> Why does this only work for mach-virt? > > Due to re-init pc becomes zero which is fine for mach-virt but > may not work for some other machine type. That is the correct reset value for the CPU (assuming no hivecs); it should be fine for everything. (Supporting a CPU with hivecs enabled from reset would probably require an extra VCPU_INIT feature flag, but it would only be relevant for AArch32 anyway and we can deal with that if we ever have a board that actually needs it.) > This brings me back to the question that are we going to > allow any other machine type with KVM ARM/ARM64 ? Of course. For 32 bit KVM/ARM we already support vexpress-a15 and I see no reason why midway or any other implemented A15 board should not work too. For 64-bit we happen not to have any board models other than virt, but if anybody contributes one it should also work just fine with KVM. thanks -- PMM _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
