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, 141 insertions, 0 deletions

diff --git a/tools/testing/vma/shared.h b/tools/testing/vma/shared.h
new file mode 100644
index 000000000..97cd7a679
--- /dev/null
+++ b/tools/testing/vma/shared.h
@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "generated/bit-length.h"
+#include "maple-shared.h"
+#include "vma_internal.h"
+#include "../../../mm/vma.h"
+
+/* Simple test runner. Assumes local num_[fail, tests] counters. */
+#define TEST(name)							\
+	do {								\
+		(*num_tests)++;						\
+		if (!test_##name()) {					\
+			(*num_fail)++;					\
+			fprintf(stderr, "Test " #name " FAILED\n");	\
+		}							\
+	} while (0)
+
+#define __ASSERT_TRUE(_expr, _fmt, ...)					   \
+	do {								   \
+		if (!(_expr)) {						   \
+			fprintf(stderr,					   \
+				"Assert FAILED at %s:%d:%s(): %s is FALSE" \
+				_fmt ".\n",				   \
+				__FILE__, __LINE__, __FUNCTION__, #_expr   \
+				__VA_OPT__(,) __VA_ARGS__);		   \
+			return false;					   \
+		}							   \
+	} while (0)
+
+#define __TO_SCALAR(x)	((unsigned long long)(uintptr_t)(x))
+
+#define ASSERT_TRUE(_expr) __ASSERT_TRUE(_expr, "")
+#define ASSERT_FALSE(_expr) ASSERT_TRUE(!(_expr))
+#define ASSERT_EQ(_val1, _val2) do {				 \
+	__typeof__(_val1) __val1 = (_val1);			 \
+	__typeof__(_val2) __val2 = (_val2);			 \
+	__ASSERT_TRUE(__val1 == __val2, " (0x%llx != 0x%llx)",	 \
+		      __TO_SCALAR(__val1), __TO_SCALAR(__val2)); \
+	} while (0)
+
+#define ASSERT_NE(_val1, _val2) do {				 \
+	__typeof__(_val1) __val1 = (_val1);			 \
+	__typeof__(_val2) __val2 = (_val2);			 \
+	__ASSERT_TRUE(__val1 != __val2, " (0x%llx == 0x%llx)",	 \
+		      __TO_SCALAR(__val1), __TO_SCALAR(__val2)); \
+	} while (0)
+
+#define ASSERT_FLAGS_SAME_MASK(_flags, _flags_other) \
+	ASSERT_TRUE(vma_flags_same_mask((_flags), (_flags_other)))
+
+#define ASSERT_FLAGS_NOT_SAME_MASK(_flags, _flags_other) \
+	ASSERT_FALSE(vma_flags_same_mask((_flags), (_flags_other)))
+
+#define ASSERT_FLAGS_SAME(_flags, ...) \
+	ASSERT_TRUE(vma_flags_same(_flags, __VA_ARGS__))
+
+#define ASSERT_FLAGS_NOT_SAME(_flags, ...) \
+	ASSERT_FALSE(vma_flags_same(_flags, __VA_ARGS__))
+
+#define ASSERT_FLAGS_EMPTY(_flags) \
+	ASSERT_TRUE(vma_flags_empty(_flags))
+
+#define ASSERT_FLAGS_NONEMPTY(_flags) \
+	ASSERT_FALSE(vma_flags_empty(_flags))
+
+extern bool fail_prealloc;
+
+/* Override vma_iter_prealloc() so we can choose to fail it. */
+#define vma_iter_prealloc(vmi, vma)					\
+	(fail_prealloc ? -ENOMEM : mas_preallocate(&(vmi)->mas, (vma), GFP_KERNEL))
+
+#define CONFIG_DEFAULT_MMAP_MIN_ADDR 65536
+
+extern unsigned long mmap_min_addr;
+extern unsigned long dac_mmap_min_addr;
+extern unsigned long stack_guard_gap;
+
+extern const struct vm_operations_struct vma_dummy_vm_ops;
+extern struct anon_vma dummy_anon_vma;
+extern struct task_struct __current;
+
+/*
+ * Helper function which provides a wrapper around a merge existing VMA
+ * operation.
+ *
+ * Declared in main.c as uses static VMA function.
+ */
+struct vm_area_struct *merge_existing(struct vma_merge_struct *vmg);
+
+/*
+ * Helper function to allocate a VMA and link it to the tree.
+ *
+ * Declared in main.c as uses static VMA function.
+ */
+int attach_vma(struct mm_struct *mm, struct vm_area_struct *vma);
+
+/* Helper function providing a dummy vm_ops->close() method.*/
+static inline void dummy_close(struct vm_area_struct *)
+{
+}
+
+/* Helper function to simply allocate a VMA. */
+struct vm_area_struct *alloc_vma(struct mm_struct *mm,
+		unsigned long start, unsigned long end,
+		pgoff_t pgoff, vma_flags_t vma_flags);
+
+/* Helper function to detach and free a VMA. */
+void detach_free_vma(struct vm_area_struct *vma);
+
+/* Helper function to allocate a VMA and link it to the tree. */
+struct vm_area_struct *alloc_and_link_vma(struct mm_struct *mm,
+		unsigned long start, unsigned long end,
+		pgoff_t pgoff, vma_flags_t vma_flags);
+
+/*
+ * Helper function to reset the dummy anon_vma to indicate it has not been
+ * duplicated.
+ */
+void reset_dummy_anon_vma(void);
+
+/*
+ * Helper function to remove all VMAs and destroy the maple tree associated with
+ * a virtual address space. Returns a count of VMAs in the tree.
+ */
+int cleanup_mm(struct mm_struct *mm, struct vma_iterator *vmi);
+
+/* Helper function to determine if VMA has had vma_start_write() performed. */
+bool vma_write_started(struct vm_area_struct *vma);
+
+void __vma_set_dummy_anon_vma(struct vm_area_struct *vma,
+		struct anon_vma_chain *avc, struct anon_vma *anon_vma);
+
+/* Provide a simple dummy VMA/anon_vma dummy setup for testing. */
+void vma_set_dummy_anon_vma(struct vm_area_struct *vma,
+			    struct anon_vma_chain *avc);