On Thu, Jun 29, 2023 at 01:50:40PM -0700, Axel Rasmussen wrote:
Just describe the feature at a really basic level.
Signed-off-by: Axel Rasmussen axelrasmussen@google.com
The final enablement of the feature can be squashed into this doc update patch too.
Acked-by: Peter Xu peterx@redhat.com
Documentation/admin-guide/mm/userfaultfd.rst | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst index 7c304e432205..b19053436369 100644 --- a/Documentation/admin-guide/mm/userfaultfd.rst +++ b/Documentation/admin-guide/mm/userfaultfd.rst @@ -244,6 +244,21 @@ write-protected (so future writes will also result in a WP fault). These ioctls support a mode flag (``UFFDIO_COPY_MODE_WP`` or ``UFFDIO_CONTINUE_MODE_WP`` respectively) to configure the mapping this way. +Memory Poisioning Emulation +---------------------------
+In response to a fault (either missing or minor), an action userspace can +take to "resolve" it is to issue a ``UFFDIO_POISON``. This will cause any +future faulters to either get a SIGBUS, or in KVM's case the guest will +receive an MCE as if there were hardware memory poisoning.
+This is used to emulate hardware memory poisoning. Imagine a VM running on a +machine which experiences a real hardware memory error. Later, we live migrate +the VM to another physical machine. Since we want the migration to be +transparent to the guest, we want that same address range to act as if it was +still poisoned, even though it's on a new physical host which ostentisbly +doesn't have a memory error in the exact same spot.
QEMU/KVM
2.41.0.255.g8b1d071c50-goog