On Wed, Sep 09, 2020 at 04:53:02PM +0100, Peter Maydell wrote: > On Wed, 9 Sep 2020 at 16:48, Andrew Jones <drjones@xxxxxxxxxx> wrote: > > We either need a KVM cap or a new CPU feature probing interface to avoid > > making userspace try features one at a time. It's too bad that VCPU_INIT > > doesn't clear all offending features from the feature set when returning > > EINVAL, because then userspace could create a scratch VCPU with everything > > it supports in order to see what KVM also supports in one go. > > You could add one if you wanted -- add a new feature bit > TELL_ME_WHAT_YOU_HAVE. If the kernel sees that then on filure > it clears out feature bits it doesn't support and also clears > TELL_ME_WHAT_YOU_HAVE. If QEMU sees EINVAL and TELL_ME_WHAT_YOU_HAVE > is still set, then it knows it's dealing with an old kernel > and has to do one-at-a-time probing. If it sees EINVAL but not > TELL_ME_WHAT_YOU_HAVE then it knows it has a new kernel and > has just got all the info. > That's a great proposal. I'll try to find time to send the patches. Thanks, drew _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
