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, 42 insertions, 0 deletions

diff --git a/Documentation/networking/seg6-sysctl.rst b/Documentation/networking/seg6-sysctl.rst
new file mode 100644
index 000000000..1b6af4779
--- /dev/null
+++ b/Documentation/networking/seg6-sysctl.rst
@@ -0,0 +1,42 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====================
+Seg6 Sysfs variables
+====================
+
+
+/proc/sys/net/conf/<iface>/seg6_* variables:
+============================================
+
+seg6_enabled - BOOL
+	Accept or drop SR-enabled IPv6 packets on this interface.
+
+	Relevant packets are those with SRH present and DA = local.
+
+	* 0 - disabled (default)
+	* not 0 - enabled
+
+seg6_require_hmac - INTEGER
+	Define HMAC policy for ingress SR-enabled packets on this interface.
+
+	* -1 - Ignore HMAC field
+	* 0 - Accept SR packets without HMAC, validate SR packets with HMAC
+	* 1 - Drop SR packets without HMAC, validate SR packets with HMAC
+
+	Default is 0.
+
+/proc/sys/net/ipv6/seg6_* variables:
+====================================
+
+seg6_flowlabel - INTEGER
+	Controls the behaviour of computing the flowlabel of outer
+	IPv6 header in case of SR T.encaps
+
+	 == =======================================================
+	 -1  set flowlabel to zero.
+	  0  copy flowlabel from Inner packet in case of Inner IPv6
+	     (Set flowlabel to 0 in case IPv4/L2)
+	  1  Compute the flowlabel using seg6_make_flowlabel()
+	 == =======================================================
+
+	Default is 0.