On May 30, 2013, at 10:07 AM, David Daney wrote: > On 05/28/2013 09:34 AM, Paolo Bonzini wrote: >> Il 19/05/2013 07:47, Sanjay Lal ha scritto: >>> - Add API to allow clients (QEMU etc.) to check whether the H/W >>> supports the MIPS VZ-ASE. >> >> Why does this matter to userspace? Do the userspace have some way to >> detect if the kernel is unmodified or minimally-modified? >> > > There are (will be) two types of VM presented by MIPS KVM: > > 1) That provided by the initial patch where a faux-MIPS is emulated and all kernel code must be in the USEG address space. > > 2) Real MIPS, addressing works as per the architecture specification. > > Presumably the user-space client would like to know which of these are supported, as well as be able to select the desired model. > > I don't know the best way to do this, but I agree that KVM_CAP_MIPS_VZ_ASE is probably not the best name for it. > > My idea was to have the arg of the KVM_CREATE_VM ioctl specify the desired style > > David Daney > > Hi Paolo, just wanted to add to David's comments. KVM/MIPS currently supports the two modes David mentioned, based on a kernel config option. KVM_CAP_MIPS_VZ_ASE is used by QEMU to make sure that the kvm module currently loaded supports the H/W virtualization. Its a bit cumbersome on MIPS, because you really can't fall back to trap and emulate, since the guest kernel for trap and emulate has a user mode link address. I am open to other ways of doing this. Regards Sanjay
