Subject: [PATCH v3 0/4] Migrate non-migrated pages of a SVM.

From: Ram Pai <[email-masked]>
Date: Fri, 19 Jun 2020 15:43:38 -0700

The time taken to switch a VM to Secure-VM, increases by the size of the VM.  A
100GB VM takes about 7minutes. This is unacceptable.  This linear increase is
caused by a suboptimal behavior by the Ultravisor and the Hypervisor.  The
Ultravisor unnecessarily migrates all the GFN of the VM from normal-memory to
secure-memory. It has to just migrate the necessary and sufficient GFNs.

However when the optimization is incorporated in the Ultravisor, the Hypervisor
starts misbehaving. The Hypervisor has a inbuilt assumption that the Ultravisor
will explicitly request to migrate, each and every GFN of the VM. If only
necessary and sufficient GFNs are requested for migration, the Hypervisor
continues to manage the remaining GFNs as normal GFNs. This leads of memory
corruption, manifested consistently when the SVM reboots.

The same is true, when a memory slot is hotplugged into a SVM. The Hypervisor
expects the ultravisor to request migration of all GFNs to secure-GFN.  But at
the same time, the hypervisor is unable to handle any H_SVM_PAGE_IN requests
from the Ultravisor, done in the context of UV_REGISTER_MEM_SLOT ucall.  This
problem manifests as random errors in the SVM, when a memory-slot is
hotplugged.

This patch series automatically migrates the non-migrated pages of a SVM,
     and thus solves the problem.

Testing: Passed rigorous SVM test using various sized SVMs.

Changelog:

v2: . fixed a bug observed by Laurent. The state of the GFN's associated
	with Secure-VMs were not reset during memslot flush.
    . Re-organized the code, for easier review.
    . Better description of the patch series.

v1: fixed a bug observed by Bharata. Pages that where paged-in and later
paged-out must also be skipped from migration during H_SVM_INIT_DONE.

Laurent Dufour (1):
  KVM: PPC: Book3S HV: migrate hot plugged memory

Ram Pai (3):
  KVM: PPC: Book3S HV: Fix function definition in book3s_hv_uvmem.c
  KVM: PPC: Book3S HV: track the state GFNs associated with secure VMs
  KVM: PPC: Book3S HV: migrate remaining normal-GFNs to secure-GFNs in
    H_SVM_INIT_DONE

 Documentation/powerpc/ultravisor.rst        |   2 +
 arch/powerpc/include/asm/kvm_book3s_uvmem.h |   2 +
 arch/powerpc/kvm/book3s_hv.c                |  10 +-
 arch/powerpc/kvm/book3s_hv_uvmem.c          | 360 +++++++++++++++++++++++-----
 4 files changed, 315 insertions(+), 59 deletions(-)

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1.8.3.1