• Dave Martin's avatar
    KVM: arm/arm64: Add KVM_ARM_VCPU_FINALIZE ioctl · 7dd32a0d
    Dave Martin authored
    Some aspects of vcpu configuration may be too complex to be
    completed inside KVM_ARM_VCPU_INIT.  Thus, there may be a
    requirement for userspace to do some additional configuration
    before various other ioctls will work in a consistent way.
    
    In particular this will be the case for SVE, where userspace will
    need to negotiate the set of vector lengths to be made available to
    the guest before the vcpu becomes fully usable.
    
    In order to provide an explicit way for userspace to confirm that
    it has finished setting up a particular vcpu feature, this patch
    adds a new ioctl KVM_ARM_VCPU_FINALIZE.
    
    When userspace has opted into a feature that requires finalization,
    typically by means of a feature flag passed to KVM_ARM_VCPU_INIT, a
    matching call to KVM_ARM_VCPU_FINALIZE is now required before
    KVM_RUN or KVM_GET_REG_LIST is allowed.  Individual features may
    impose additional restrictions where appropriate.
    
    No existing vcpu features are affected by this, so current
    userspace implementations will continue to work exactly as before,
    with no need to issue KVM_ARM_VCPU_FINALIZE.
    
    As implemented in this patch, KVM_ARM_VCPU_FINALIZE is currently a
    placeholder: no finalizable features exist yet, so ioctl is not
    required and will always yield EINVAL.  Subsequent patches will add
    the finalization logic to make use of this ioctl for SVE.
    
    No functional change for existing userspace.
    Signed-off-by: default avatarDave Martin <Dave.Martin@arm.com>
    Reviewed-by: default avatarJulien Thierry <julien.thierry@arm.com>
    Tested-by: default avatarzhang.lei <zhang.lei@jp.fujitsu.com>
    Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
    7dd32a0d
arm.c 37.4 KB