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, 103 insertions, 0 deletions

diff --git a/arch/powerpc/boot/io.h b/arch/powerpc/boot/io.h
new file mode 100644
index 000000000..5c6f90c34
--- /dev/null
+++ b/arch/powerpc/boot/io.h
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _IO_H
+#define _IO_H
+
+#include "types.h"
+
+/*
+ * Low-level I/O routines.
+ *
+ * Copied from <file:arch/powerpc/include/asm/io.h> (which has no copyright)
+ */
+static inline int in_8(const volatile unsigned char *addr)
+{
+	int ret;
+
+	__asm__ __volatile__("lbz%U1%X1 %0,%1; twi 0,%0,0; isync"
+			     : "=r" (ret) : "m" (*addr));
+	return ret;
+}
+
+static inline void out_8(volatile unsigned char *addr, int val)
+{
+	__asm__ __volatile__("stb%U0%X0 %1,%0; sync"
+			     : "=m" (*addr) : "r" (val));
+}
+
+static inline unsigned in_le16(const volatile u16 *addr)
+{
+	unsigned ret;
+
+	__asm__ __volatile__("lhbrx %0,0,%1; twi 0,%0,0; isync"
+			     : "=r" (ret) : "r" (addr), "m" (*addr));
+
+	return ret;
+}
+
+static inline unsigned in_be16(const volatile u16 *addr)
+{
+	unsigned ret;
+
+	__asm__ __volatile__("lhz%U1%X1 %0,%1; twi 0,%0,0; isync"
+			     : "=r" (ret) : "m" (*addr));
+	return ret;
+}
+
+static inline void out_le16(volatile u16 *addr, int val)
+{
+	__asm__ __volatile__("sthbrx %1,0,%2; sync" : "=m" (*addr)
+			     : "r" (val), "r" (addr));
+}
+
+static inline void out_be16(volatile u16 *addr, int val)
+{
+	__asm__ __volatile__("sth%U0%X0 %1,%0; sync"
+			     : "=m" (*addr) : "r" (val));
+}
+
+static inline unsigned in_le32(const volatile unsigned *addr)
+{
+	unsigned ret;
+
+	__asm__ __volatile__("lwbrx %0,0,%1; twi 0,%0,0; isync"
+			     : "=r" (ret) : "r" (addr), "m" (*addr));
+	return ret;
+}
+
+static inline unsigned in_be32(const volatile unsigned *addr)
+{
+	unsigned ret;
+
+	__asm__ __volatile__("lwz%U1%X1 %0,%1; twi 0,%0,0; isync"
+			     : "=r" (ret) : "m" (*addr));
+	return ret;
+}
+
+static inline void out_le32(volatile unsigned *addr, int val)
+{
+	__asm__ __volatile__("stwbrx %1,0,%2; sync" : "=m" (*addr)
+			     : "r" (val), "r" (addr));
+}
+
+static inline void out_be32(volatile unsigned *addr, int val)
+{
+	__asm__ __volatile__("stw%U0%X0 %1,%0; sync"
+			     : "=m" (*addr) : "r" (val));
+}
+
+static inline void sync(void)
+{
+	asm volatile("sync" : : : "memory");
+}
+
+static inline void eieio(void)
+{
+	asm volatile("eieio" : : : "memory");
+}
+
+static inline void barrier(void)
+{
+	asm volatile("" : : : "memory");
+}
+
+#endif /* _IO_H */