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, 308 insertions, 0 deletions

diff --git a/drivers/acpi/acpica/exdebug.c b/drivers/acpi/acpica/exdebug.c
new file mode 100644
index 000000000..a592bcc5d
--- /dev/null
+++ b/drivers/acpi/acpica/exdebug.c
@@ -0,0 +1,308 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/******************************************************************************
+ *
+ * Module Name: exdebug - Support for stores to the AML Debug Object
+ *
+ * Copyright (C) 2000 - 2026, Intel Corp.
+ *
+ *****************************************************************************/
+
+#include <acpi/acpi.h>
+#include "accommon.h"
+#include "acinterp.h"
+
+#define _COMPONENT          ACPI_EXECUTER
+ACPI_MODULE_NAME("exdebug")
+
+#ifndef ACPI_NO_ERROR_MESSAGES
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ex_do_debug_object
+ *
+ * PARAMETERS:  source_desc         - Object to be output to "Debug Object"
+ *              level               - Indentation level (used for packages)
+ *              index               - Current package element, zero if not pkg
+ *
+ * RETURN:      None
+ *
+ * DESCRIPTION: Handles stores to the AML Debug Object. For example:
+ *              Store(INT1, Debug)
+ *
+ * This function is not compiled if ACPI_NO_ERROR_MESSAGES is set.
+ *
+ * This function is only enabled if acpi_gbl_enable_aml_debug_object is set, or
+ * if ACPI_LV_DEBUG_OBJECT is set in the acpi_dbg_level. Thus, in the normal
+ * operational case, stores to the debug object are ignored but can be easily
+ * enabled if necessary.
+ *
+ ******************************************************************************/
+void
+acpi_ex_do_debug_object(union acpi_operand_object *source_desc,
+			u32 level, u32 index)
+{
+	u32 i;
+	u32 timer;
+	union acpi_operand_object *object_desc;
+	u32 value;
+
+	ACPI_FUNCTION_TRACE_PTR(ex_do_debug_object, source_desc);
+
+	/* Output must be enabled via the debug_object global or the dbg_level */
+
+	if (!acpi_gbl_enable_aml_debug_object &&
+	    !(acpi_dbg_level & ACPI_LV_DEBUG_OBJECT)) {
+		return_VOID;
+	}
+
+	/* Newline -- don't emit the line header */
+
+	if (source_desc &&
+	    (ACPI_GET_DESCRIPTOR_TYPE(source_desc) == ACPI_DESC_TYPE_OPERAND) &&
+	    (source_desc->common.type == ACPI_TYPE_STRING)) {
+		if ((source_desc->string.length == 1) &&
+		    (*source_desc->string.pointer == '\n')) {
+			acpi_os_printf("\n");
+			return_VOID;
+		}
+	}
+
+	/*
+	 * Print line header as long as we are not in the middle of an
+	 * object display
+	 */
+	if (!((level > 0) && index == 0)) {
+		if (acpi_gbl_display_debug_timer) {
+			/*
+			 * We will emit the current timer value (in microseconds) with each
+			 * debug output. Only need the lower 26 bits. This allows for 67
+			 * million microseconds or 67 seconds before rollover.
+			 *
+			 * Convert 100 nanosecond units to microseconds
+			 */
+			timer = ((u32)acpi_os_get_timer() / 10);
+			timer &= 0x03FFFFFF;
+
+			acpi_os_printf("ACPI Debug: T=0x%8.8X %*s", timer,
+				       level, " ");
+		} else {
+			acpi_os_printf("ACPI Debug: %*s", level, " ");
+		}
+	}
+
+	/* Display the index for package output only */
+
+	if (index > 0) {
+		acpi_os_printf("(%.2u) ", index - 1);
+	}
+
+	if (!source_desc) {
+		acpi_os_printf("[Null Object]\n");
+		return_VOID;
+	}
+
+	if (ACPI_GET_DESCRIPTOR_TYPE(source_desc) == ACPI_DESC_TYPE_OPERAND) {
+
+		/* No object type prefix needed for integers and strings */
+
+		if ((source_desc->common.type != ACPI_TYPE_INTEGER) &&
+		    (source_desc->common.type != ACPI_TYPE_STRING)) {
+			acpi_os_printf("%s ",
+				       acpi_ut_get_object_type_name
+				       (source_desc));
+		}
+
+		if (!acpi_ut_valid_internal_object(source_desc)) {
+			acpi_os_printf("%p, Invalid Internal Object!\n",
+				       source_desc);
+			return_VOID;
+		}
+	} else if (ACPI_GET_DESCRIPTOR_TYPE(source_desc) ==
+		   ACPI_DESC_TYPE_NAMED) {
+		acpi_os_printf("%s (Node %p)\n",
+			       acpi_ut_get_type_name(((struct
+						       acpi_namespace_node *)
+						      source_desc)->type),
+			       source_desc);
+		return_VOID;
+	} else {
+		return_VOID;
+	}
+
+	/* source_desc is of type ACPI_DESC_TYPE_OPERAND */
+
+	switch (source_desc->common.type) {
+	case ACPI_TYPE_INTEGER:
+
+		/* Output correct integer width */
+
+		if (acpi_gbl_integer_byte_width == 4) {
+			acpi_os_printf("0x%8.8X\n",
+				       (u32)source_desc->integer.value);
+		} else {
+			acpi_os_printf("0x%8.8X%8.8X\n",
+				       ACPI_FORMAT_UINT64(source_desc->integer.
+							  value));
+		}
+		break;
+
+	case ACPI_TYPE_BUFFER:
+
+		acpi_os_printf("[0x%.2X]\n", (u32)source_desc->buffer.length);
+		acpi_ut_dump_buffer(source_desc->buffer.pointer,
+				    (source_desc->buffer.length < 256) ?
+				    source_desc->buffer.length : 256,
+				    DB_BYTE_DISPLAY, 0);
+		break;
+
+	case ACPI_TYPE_STRING:
+
+		acpi_os_printf("\"%s\"\n", source_desc->string.pointer);
+		break;
+
+	case ACPI_TYPE_PACKAGE:
+
+		acpi_os_printf("(Contains 0x%.2X Elements):\n",
+			       source_desc->package.count);
+
+		/* Output the entire contents of the package */
+
+		for (i = 0; i < source_desc->package.count; i++) {
+			acpi_ex_do_debug_object(source_desc->package.
+						elements[i], level + 4, i + 1);
+		}
+		break;
+
+	case ACPI_TYPE_LOCAL_REFERENCE:
+
+		acpi_os_printf("[%s] ",
+			       acpi_ut_get_reference_name(source_desc));
+
+		/* Decode the reference */
+
+		switch (source_desc->reference.class) {
+		case ACPI_REFCLASS_INDEX:
+
+			acpi_os_printf("0x%X\n", source_desc->reference.value);
+			break;
+
+		case ACPI_REFCLASS_TABLE:
+
+			/* Case for ddb_handle */
+
+			acpi_os_printf("Table Index 0x%X\n",
+				       source_desc->reference.value);
+			return_VOID;
+
+		default:
+
+			break;
+		}
+
+		acpi_os_printf(" ");
+
+		/* Check for valid node first, then valid object */
+
+		if (source_desc->reference.node) {
+			if (ACPI_GET_DESCRIPTOR_TYPE
+			    (source_desc->reference.node) !=
+			    ACPI_DESC_TYPE_NAMED) {
+				acpi_os_printf
+				    (" %p - Not a valid namespace node\n",
+				     source_desc->reference.node);
+			} else {
+				acpi_os_printf("Node %p [%4.4s] ",
+					       source_desc->reference.node,
+					       (source_desc->reference.node)->
+					       name.ascii);
+
+				switch ((source_desc->reference.node)->type) {
+
+					/* These types have no attached object */
+
+				case ACPI_TYPE_DEVICE:
+					acpi_os_printf("Device\n");
+					break;
+
+				case ACPI_TYPE_THERMAL:
+					acpi_os_printf("Thermal Zone\n");
+					break;
+
+				default:
+
+					acpi_ex_do_debug_object((source_desc->
+								 reference.
+								 node)->object,
+								level + 4, 0);
+					break;
+				}
+			}
+		} else if (source_desc->reference.object) {
+			if (ACPI_GET_DESCRIPTOR_TYPE
+			    (source_desc->reference.object) ==
+			    ACPI_DESC_TYPE_NAMED) {
+
+				/* Reference object is a namespace node */
+
+				acpi_ex_do_debug_object(ACPI_CAST_PTR
+							(union
+							 acpi_operand_object,
+							 source_desc->reference.
+							 object), level + 4, 0);
+			} else {
+				object_desc = source_desc->reference.object;
+				value = source_desc->reference.value;
+
+				switch (object_desc->common.type) {
+				case ACPI_TYPE_BUFFER:
+
+					acpi_os_printf("Buffer[%u] = 0x%2.2X\n",
+						       value,
+						       *source_desc->reference.
+						       index_pointer);
+					break;
+
+				case ACPI_TYPE_STRING:
+
+					acpi_os_printf
+					    ("String[%u] = \"%c\" (0x%2.2X)\n",
+					     value,
+					     *source_desc->reference.
+					     index_pointer,
+					     *source_desc->reference.
+					     index_pointer);
+					break;
+
+				case ACPI_TYPE_PACKAGE:
+
+					acpi_os_printf("Package[%u] = ", value);
+					if (!(*source_desc->reference.where)) {
+						acpi_os_printf
+						    ("[Uninitialized Package Element]\n");
+					} else {
+						acpi_ex_do_debug_object
+						    (*source_desc->reference.
+						     where, level + 4, 0);
+					}
+					break;
+
+				default:
+
+					acpi_os_printf
+					    ("Unknown Reference object type %X\n",
+					     object_desc->common.type);
+					break;
+				}
+			}
+		}
+		break;
+
+	default:
+
+		acpi_os_printf("(Descriptor %p)\n", source_desc);
+		break;
+	}
+
+	ACPI_DEBUG_PRINT_RAW((ACPI_DB_EXEC, "\n"));
+	return_VOID;
+}
+#endif