On Thu, Sep 5, 2013 at 8:21 PM, Peter Maydell <peter.maydell@xxxxxxxxxx> wrote: > On 5 September 2013 15:45, Anup Patel <anup.patel@xxxxxxxxxx> wrote: >> It will be very useful for user space if it has a method for specifying >> KVM ARM/ARM64 to give a VCPU with target type suitable to underlying host >> but with particular set of features. >> >> In other words, user space might not be interested in having a particular >> target type for VCPU but it will certainely want particular set of features >> in the VCPU. >> >> The patch tries to implement above described method of specifying VCPU >> target CPU=Host from user space by extending the KVM_ARM_VCPU_INIT ioctl >> and having a dummy target KVM_ARM_TARGET_HOST which means Target CPU >> same as (or suitable to) underlying host. > > I thought the consensus on the call last week was > to have an ioctl for "get best CPU for this host" > and then for userspace to pass that value to > VCPU_INIT ? I had considered having a separate ioctl for "get best CPU for this host" (as per KVM call minutes) but the same thing is possible with existing KVM_ARM_VCPU_INIT so why not extend this ioctl. Also, I was finding it hard to come up with a use case where having a separate ioctl for "get best CPU for this host" would be better for user space. Further, the approach proposed by this patch also makes the KVM_ARM_VCPU_INIT ioctl inline with what we do for KVM x86 that is provide only a set of features user space wish and KVM x86 will try to provide most of those features with a virtual CPU suitable to host. Another advantage I saw in extending KVM_ARM_VCPU_INIT ioctl is backward compatibility with current semantics. In other words, this patch does not break current KVMTOOL/QEMU and they can implement "-cpu host" whenever they wish without using any additional ioctl. PFA, KVMTOOL patch which I used to test KVM_ARM_TARGET_HOST. > > -- PMM > _______________________________________________ > kvmarm mailing list > kvmarm@xxxxxxxxxxxxxxxxxxxxx > https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm --Anup
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