Le 21/07/2020 à 23:37, Ram Pai a écrit :
On Tue, Jul 21, 2020 at 12:42:02PM +0200, Laurent Dufour wrote:
When a secure memslot is dropped, all the pages backed in the secure device
(aka really backed by secure memory by the Ultravisor) should be paged out
to a normal page. Previously, this was achieved by triggering the page
fault mechanism which is calling kvmppc_svm_page_out() on each pages.
This can't work when hot unplugging a memory slot because the memory slot
is flagged as invalid and gfn_to_pfn() is then not trying to access the
page, so the page fault mechanism is not triggered.
Since the final goal is to make a call to kvmppc_svm_page_out() it seems
simpler to directly calling it instead of triggering such a mechanism. This
^^ call directly instead of triggering..
way kvmppc_uvmem_drop_pages() can be called even when hot unplugging a
memslot.
Since kvmppc_uvmem_drop_pages() is already holding kvm->arch.uvmem_lock,
the call to __kvmppc_svm_page_out() is made.
As __kvmppc_svm_page_out needs the vma pointer to migrate the pages, the
VMA is fetched in a lazy way, to not trigger find_vma() all the time. In
addition, the mmap_sem is help in read mode during that time, not in write
^^ held
mode since the virual memory layout is not impacted, and
kvm->arch.uvmem_lock prevents concurrent operation on the secure device.
Cc: Ram Pai <linuxram@xxxxxxxxxx>
Reviewed-by: Ram Pai <linuxram@xxxxxxxxxx>
Thanks for reviewing this series.
Regarding the wordsmithing, Paul, could you manage that when pulling the series?
Thanks,
Laurent.
