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, 62 insertions, 0 deletions

diff --git a/include/uapi/asm-generic/resource.h b/include/uapi/asm-generic/resource.h
new file mode 100644
index 000000000..f12db7a0d
--- /dev/null
+++ b/include/uapi/asm-generic/resource.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_ASM_GENERIC_RESOURCE_H
+#define _UAPI_ASM_GENERIC_RESOURCE_H
+
+/*
+ * Resource limit IDs
+ *
+ * ( Compatibility detail: there are architectures that have
+ *   a different rlimit ID order in the 5-9 range and want
+ *   to keep that order for binary compatibility. The reasons
+ *   are historic and all new rlimits are identical across all
+ *   arches. If an arch has such special order for some rlimits
+ *   then it defines them prior including asm-generic/resource.h. )
+ */
+
+#define RLIMIT_CPU		0	/* CPU time in sec */
+#define RLIMIT_FSIZE		1	/* Maximum filesize */
+#define RLIMIT_DATA		2	/* max data size */
+#define RLIMIT_STACK		3	/* max stack size */
+#define RLIMIT_CORE		4	/* max core file size */
+
+#ifndef RLIMIT_RSS
+# define RLIMIT_RSS		5	/* max resident set size */
+#endif
+
+#ifndef RLIMIT_NPROC
+# define RLIMIT_NPROC		6	/* max number of processes */
+#endif
+
+#ifndef RLIMIT_NOFILE
+# define RLIMIT_NOFILE		7	/* max number of open files */
+#endif
+
+#ifndef RLIMIT_MEMLOCK
+# define RLIMIT_MEMLOCK		8	/* max locked-in-memory address space */
+#endif
+
+#ifndef RLIMIT_AS
+# define RLIMIT_AS		9	/* address space limit */
+#endif
+
+#define RLIMIT_LOCKS		10	/* maximum file locks held */
+#define RLIMIT_SIGPENDING	11	/* max number of pending signals */
+#define RLIMIT_MSGQUEUE		12	/* maximum bytes in POSIX mqueues */
+#define RLIMIT_NICE		13	/* max nice prio allowed to raise to
+					   0-39 for nice level 19 .. -20 */
+#define RLIMIT_RTPRIO		14	/* maximum realtime priority */
+#define RLIMIT_RTTIME		15	/* timeout for RT tasks in us */
+#define RLIM_NLIMITS		16
+
+/*
+ * SuS says limits have to be unsigned.
+ * Which makes a ton more sense anyway.
+ *
+ * Some architectures override this (for compatibility reasons):
+ */
+#ifndef RLIM_INFINITY
+# define RLIM_INFINITY		(~0UL)
+#endif
+
+
+#endif /* _UAPI_ASM_GENERIC_RESOURCE_H */