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, 57 insertions, 0 deletions

diff --git a/Documentation/networking/mpls-sysctl.rst b/Documentation/networking/mpls-sysctl.rst
new file mode 100644
index 000000000..0a2ac8840
--- /dev/null
+++ b/Documentation/networking/mpls-sysctl.rst
@@ -0,0 +1,57 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====================
+MPLS Sysfs variables
+====================
+
+/proc/sys/net/mpls/* Variables:
+===============================
+
+platform_labels - INTEGER
+	Number of entries in the platform label table.  It is not
+	possible to configure forwarding for label values equal to or
+	greater than the number of platform labels.
+
+	A dense utilization of the entries in the platform label table
+	is possible and expected as the platform labels are locally
+	allocated.
+
+	If the number of platform label table entries is set to 0 no
+	label will be recognized by the kernel and mpls forwarding
+	will be disabled.
+
+	Reducing this value will remove all label routing entries that
+	no longer fit in the table.
+
+	Possible values: 0 - 1048575
+
+	Default: 0
+
+ip_ttl_propagate - BOOL
+	Control whether TTL is propagated from the IPv4/IPv6 header to
+	the MPLS header on imposing labels and propagated from the
+	MPLS header to the IPv4/IPv6 header on popping the last label.
+
+	If disabled, the MPLS transport network will appear as a
+	single hop to transit traffic.
+
+	* 0 - disabled / RFC 3443 [Short] Pipe Model
+	* 1 - enabled / RFC 3443 Uniform Model (default)
+
+default_ttl - INTEGER
+	Default TTL value to use for MPLS packets where it cannot be
+	propagated from an IP header, either because one isn't present
+	or ip_ttl_propagate has been disabled.
+
+	Possible values: 1 - 255
+
+	Default: 255
+
+conf/<interface>/input - BOOL
+	Control whether packets can be input on this interface.
+
+	If disabled, packets will be discarded without further
+	processing.
+
+	* 0 - disabled (default)
+	* not 0 - enabled