KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 192 insertions, 0 deletions

diff --git a/Documentation/admin-guide/index.rst b/Documentation/admin-guide/index.rst
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+=================================================
+The Linux kernel user's and administrator's guide
+=================================================
+
+The following is a collection of user-oriented documents that have been
+added to the kernel over time.  There is, as yet, little overall order or
+organization here — this material was not written to be a single, coherent
+document!  With luck things will improve quickly over time.
+
+General guides to kernel administration
+---------------------------------------
+
+This initial section contains overall information, including the README
+file describing the kernel as a whole, documentation on kernel parameters,
+etc.
+
+.. toctree::
+   :maxdepth: 1
+
+   README
+   devices
+
+   features
+
+A big part of the kernel's administrative interface is the /proc and sysfs
+virtual filesystems; these documents describe how to interact with tem
+
+.. toctree::
+   :maxdepth: 1
+
+   sysfs-rules
+   sysctl/index
+   cputopology
+   abi
+
+Security-related documentation:
+
+.. toctree::
+   :maxdepth: 1
+
+   hw-vuln/index
+   LSM/index
+   perf-security
+
+Booting the kernel
+------------------
+
+.. toctree::
+   :maxdepth: 1
+
+   bootconfig
+   kernel-parameters
+   efi-stub
+   initrd
+
+
+Tracking down and identifying problems
+--------------------------------------
+
+Here is a set of documents aimed at users who are trying to track down
+problems and bugs in particular.
+
+.. toctree::
+   :maxdepth: 1
+
+   reporting-issues
+   reporting-regressions
+   quickly-build-trimmed-linux
+   verify-bugs-and-bisect-regressions
+   bug-hunting
+   bug-bisect
+   tainted-kernels
+   ramoops
+   dynamic-debug-howto
+   init
+   kdump/index
+   perf/index
+   pstore-blk
+   clearing-warn-once
+   kernel-per-CPU-kthreads
+   lockup-watchdogs
+   RAS/index
+   sysrq
+
+
+Core-kernel subsystems
+----------------------
+
+These documents describe core-kernel administration interfaces that are
+likely to be of interest on almost any system.
+
+.. toctree::
+   :maxdepth: 1
+
+   cgroup-v2
+   cgroup-v1/index
+   cpu-isolation
+   cpu-load
+   mm/index
+   module-signing
+   namespaces/index
+   numastat
+   pm/index
+   syscall-user-dispatch
+
+Support for non-native binary formats.  Note that some of these
+documents are ... old ...
+
+.. toctree::
+   :maxdepth: 1
+
+   binfmt-misc
+   java
+   mono
+
+
+Block-layer and filesystem administration
+-----------------------------------------
+
+.. toctree::
+   :maxdepth: 1
+
+   bcache
+   binderfs
+   blockdev/index
+   cifs/index
+   device-mapper/index
+   ext4
+   filesystem-monitoring
+   nfs/index
+   iostats
+   jfs
+   md
+   ufs
+   xfs
+
+Device-specific guides
+----------------------
+
+How to configure your hardware within your Linux system.
+
+.. toctree::
+   :maxdepth: 1
+
+   acpi/index
+   aoe/index
+   auxdisplay/index
+   braille-console
+   btmrvl
+   dell_rbu
+   edid
+   gpio/index
+   hw_random
+   laptops/index
+   lcd-panel-cgram
+   media/index
+   nvme-multipath
+   parport
+   pnp
+   rapidio
+   rtc
+   serial-console
+   svga
+   thermal/index
+   thunderbolt
+   vga-softcursor
+   video-output
+
+Workload analysis
+-----------------
+
+This is the beginning of a section with information of interest to
+application developers and system integrators doing analysis of the
+Linux kernel for safety critical applications. Documents supporting
+analysis of kernel interactions with applications, and key kernel
+subsystems expectations will be found here.
+
+.. toctree::
+   :maxdepth: 1
+
+   workload-tracing
+
+Everything else
+---------------
+
+A few hard-to-categorize and generally obsolete documents.
+
+.. toctree::
+   :maxdepth: 1
+
+   ldm
+   unicode