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>

2 files changed, 41 insertions, 0 deletions

diff --git a/Documentation/userspace-api/ebpf/index.rst b/Documentation/userspace-api/ebpf/index.rst
new file mode 100644
index 000000000..473dfba78
--- /dev/null
+++ b/Documentation/userspace-api/ebpf/index.rst
@@ -0,0 +1,17 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+eBPF Userspace API
+==================
+
+eBPF is a kernel mechanism to provide a sandboxed runtime environment in the
+Linux kernel for runtime extension and instrumentation without changing kernel
+source code or loading kernel modules. eBPF programs can be attached to various
+kernel subsystems, including networking, tracing and Linux security modules
+(LSM).
+
+For internal kernel documentation on eBPF, see Documentation/bpf/index.rst.
+
+.. toctree::
+   :maxdepth: 1
+
+   syscall
diff --git a/Documentation/userspace-api/ebpf/syscall.rst b/Documentation/userspace-api/ebpf/syscall.rst
new file mode 100644
index 000000000..ea9918084
--- /dev/null
+++ b/Documentation/userspace-api/ebpf/syscall.rst
@@ -0,0 +1,24 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+eBPF Syscall
+------------
+
+:Authors: - Alexei Starovoitov <ast@kernel.org>
+          - Joe Stringer <joe@wand.net.nz>
+          - Michael Kerrisk <mtk.manpages@gmail.com>
+
+The primary info for the bpf syscall is available in the `man-pages`_
+for `bpf(2)`_.
+
+bpf() subcommand reference
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. kernel-doc:: include/uapi/linux/bpf.h
+   :doc: eBPF Syscall Preamble
+
+.. kernel-doc:: include/uapi/linux/bpf.h
+   :doc: eBPF Syscall Commands
+
+.. Links:
+.. _man-pages: https://www.kernel.org/doc/man-pages/
+.. _bpf(2): https://man7.org/linux/man-pages/man2/bpf.2.html