linux-kernel - [PATCH v2 0/2] Rework secure memslot dropping

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Date:   Tue, 21 Jul 2020 12:42:00 +0200
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        kvm-ppc@...r.kernel.org, mpe@...erman.id.au, paulus@...ba.org
Cc:     linuxram@...ibm.com, sukadev@...ux.ibm.com, bauerman@...ux.ibm.com,
        bharata@...ux.ibm.com
Subject: [PATCH v2 0/2] Rework secure memslot dropping

When doing memory hotplug on a secure VM, the secure pages are not well
cleaned from the secure device when dropping the memslot.  This silent
error, is then preventing the SVM to reboot properly after the following
sequence of commands are run in the Qemu monitor:

device_add pc-dimm,id=dimm1,memdev=mem1
device_del dimm1
device_add pc-dimm,id=dimm1,memdev=mem1

At reboot time, when the kernel is booting again and switching to the
secure mode, the page_in is failing for the pages in the memslot because
the cleanup was not done properly, because the memslot is flagged as
invalid during the hot unplug and thus the page fault mechanism is not
triggered.

To prevent that during the memslot dropping, instead of belonging on the
page fault mechanism to trigger the page out of the secured pages, it seems
simpler to directly call the function doing the page out. This way the
state of the memslot is not interfering on the page out process.

This series applies on top of the Ram's one titled:
"[v4 0/5] Migrate non-migrated pages of a SVM."
https://lore.kernel.org/linuxppc-dev/1594972827-13928-1-git-send-email-linuxram@us.ibm.com/

Changes since V1:
 - Rebase on top of Ram's V4 series
 - Address Bharata's comment to use mmap_read_*lock().

Laurent Dufour (2):
  KVM: PPC: Book3S HV: move kvmppc_svm_page_out up
  KVM: PPC: Book3S HV: rework secure mem slot dropping

 arch/powerpc/kvm/book3s_hv_uvmem.c | 220 +++++++++++++++++------------
 1 file changed, 127 insertions(+), 93 deletions(-)

-- 
2.27.0