• Bharata B Rao's avatar
    KVM: PPC: Book3S HV: Support for running secure guests · ca9f4942
    Bharata B Rao authored
    A pseries guest can be run as secure guest on Ultravisor-enabled
    POWER platforms. On such platforms, this driver will be used to manage
    the movement of guest pages between the normal memory managed by
    hypervisor (HV) and secure memory managed by Ultravisor (UV).
    
    HV is informed about the guest's transition to secure mode via hcalls:
    
    H_SVM_INIT_START: Initiate securing a VM
    H_SVM_INIT_DONE: Conclude securing a VM
    
    As part of H_SVM_INIT_START, register all existing memslots with
    the UV. H_SVM_INIT_DONE call by UV informs HV that transition of
    the guest to secure mode is complete.
    
    These two states (transition to secure mode STARTED and transition
    to secure mode COMPLETED) are recorded in kvm->arch.secure_guest.
    Setting these states will cause the assembly code that enters the
    guest to call the UV_RETURN ucall instead of trying to enter the
    guest directly.
    
    Migration of pages betwen normal and secure memory of secure
    guest is implemented in H_SVM_PAGE_IN and H_SVM_PAGE_OUT hcalls.
    
    H_SVM_PAGE_IN: Move the content of a normal page to secure page
    H_SVM_PAGE_OUT: Move the content of a secure page to normal page
    
    Private ZONE_DEVICE memory equal to the amount of secure memory
    available in the platform for running secure guests is created.
    Whenever a page belonging to the guest becomes secure, a page from
    this private device memory is used to represent and track that secure
    page on the HV side. The movement of pages between normal and secure
    memory is done via migrate_vma_pages() using UV_PAGE_IN and
    UV_PAGE_OUT ucalls.
    
    In order to prevent the device private pages (that correspond to pages
    of secure guest) from participating in KSM merging, H_SVM_PAGE_IN
    calls ksm_madvise() under read version of mmap_sem. However
    ksm_madvise() needs to be under write lock.  Hence we call
    kvmppc_svm_page_in with mmap_sem held for writing, and it then
    downgrades to a read lock after calling ksm_madvise.
    
    [paulus@ozlabs.org - roll in patch "KVM: PPC: Book3S HV: Take write
     mmap_sem when calling ksm_madvise"]
    Signed-off-by: default avatarBharata B Rao <bharata@linux.ibm.com>
    Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
    ca9f4942
Makefile 3.15 KB