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/include/uapi/asm-generic/poll.h b/include/uapi/asm-generic/poll.h
new file mode 100644
index 000000000..f9c520ce4
--- /dev/null
+++ b/include/uapi/asm-generic/poll.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __ASM_GENERIC_POLL_H
+#define __ASM_GENERIC_POLL_H
+
+/* These are specified by iBCS2 */
+#define POLLIN		0x0001
+#define POLLPRI		0x0002
+#define POLLOUT		0x0004
+#define POLLERR		0x0008
+#define POLLHUP		0x0010
+#define POLLNVAL	0x0020
+
+/* The rest seem to be more-or-less nonstandard. Check them! */
+#define POLLRDNORM	0x0040
+#define POLLRDBAND	0x0080
+#ifndef POLLWRNORM
+#define POLLWRNORM	0x0100
+#endif
+#ifndef POLLWRBAND
+#define POLLWRBAND	0x0200
+#endif
+#ifndef POLLMSG
+#define POLLMSG		0x0400
+#endif
+#ifndef POLLREMOVE
+#define POLLREMOVE	0x1000
+#endif
+#ifndef POLLRDHUP
+#define POLLRDHUP       0x2000
+#endif
+
+#define POLLFREE	(__force __poll_t)0x4000
+
+#define POLL_BUSY_LOOP	(__force __poll_t)0x8000
+
+struct pollfd {
+	int fd;
+	short events;
+	short revents;
+};
+
+#endif	/* __ASM_GENERIC_POLL_H */