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, 86 insertions, 0 deletions

diff --git a/include/xen/arm/interface.h b/include/xen/arm/interface.h
new file mode 100644
index 000000000..61360b89d
--- /dev/null
+++ b/include/xen/arm/interface.h
@@ -0,0 +1,86 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/******************************************************************************
+ * Guest OS interface to ARM Xen.
+ *
+ * Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Citrix, 2012
+ */
+
+#ifndef _ASM_ARM_XEN_INTERFACE_H
+#define _ASM_ARM_XEN_INTERFACE_H
+
+#include <linux/types.h>
+
+#define uint64_aligned_t uint64_t __attribute__((aligned(8)))
+
+#define __DEFINE_GUEST_HANDLE(name, type) \
+	typedef struct { union { type *p; uint64_aligned_t q; }; }  \
+        __guest_handle_ ## name
+
+#define DEFINE_GUEST_HANDLE_STRUCT(name) \
+	__DEFINE_GUEST_HANDLE(name, struct name)
+#define DEFINE_GUEST_HANDLE(name) __DEFINE_GUEST_HANDLE(name, name)
+#define GUEST_HANDLE(name)        __guest_handle_ ## name
+
+#define set_xen_guest_handle(hnd, val)			\
+	do {						\
+		if (sizeof(hnd) == 8)			\
+			*(uint64_t *)&(hnd) = 0;	\
+		(hnd).p = val;				\
+	} while (0)
+
+#define __HYPERVISOR_platform_op_raw __HYPERVISOR_platform_op
+
+#ifndef __ASSEMBLER__
+/* Explicitly size integers that represent pfns in the interface with
+ * Xen so that we can have one ABI that works for 32 and 64 bit guests.
+ * Note that this means that the xen_pfn_t type may be capable of
+ * representing pfn's which the guest cannot represent in its own pfn
+ * type. However since pfn space is controlled by the guest this is
+ * fine since it simply wouldn't be able to create any sure pfns in
+ * the first place.
+ */
+typedef uint64_t xen_pfn_t;
+#define PRI_xen_pfn "llx"
+typedef uint64_t xen_ulong_t;
+#define PRI_xen_ulong "llx"
+typedef int64_t xen_long_t;
+#define PRI_xen_long "llx"
+/* Guest handles for primitive C types. */
+__DEFINE_GUEST_HANDLE(uchar, unsigned char);
+__DEFINE_GUEST_HANDLE(uint,  unsigned int);
+DEFINE_GUEST_HANDLE(char);
+DEFINE_GUEST_HANDLE(int);
+DEFINE_GUEST_HANDLE(void);
+DEFINE_GUEST_HANDLE(uint64_t);
+DEFINE_GUEST_HANDLE(uint32_t);
+DEFINE_GUEST_HANDLE(xen_pfn_t);
+DEFINE_GUEST_HANDLE(xen_ulong_t);
+
+/* Maximum number of virtual CPUs in multi-processor guests. */
+#define MAX_VIRT_CPUS 1
+
+struct arch_vcpu_info { };
+struct arch_shared_info { };
+
+/* TODO: Move pvclock definitions some place arch independent */
+struct pvclock_vcpu_time_info {
+	u32   version;
+	u32   pad0;
+	u64   tsc_timestamp;
+	u64   system_time;
+	u32   tsc_to_system_mul;
+	s8    tsc_shift;
+	u8    flags;
+	u8    pad[2];
+} __attribute__((__packed__)); /* 32 bytes */
+
+/* It is OK to have a 12 bytes struct with no padding because it is packed */
+struct pvclock_wall_clock {
+	u32   version;
+	u32   sec;
+	u32   nsec;
+	u32   sec_hi;
+} __attribute__((__packed__));
+#endif
+
+#endif /* _ASM_ARM_XEN_INTERFACE_H */