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, 87 insertions, 0 deletions

diff --git a/arch/powerpc/boot/simpleboot.c b/arch/powerpc/boot/simpleboot.c
new file mode 100644
index 000000000..27591df41
--- /dev/null
+++ b/arch/powerpc/boot/simpleboot.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * The simple platform -- for booting when firmware doesn't supply a device
+ *                        tree or any platform configuration information.
+ *                        All data is extracted from an embedded device tree
+ *                        blob.
+ *
+ * Authors: Scott Wood <scottwood@freescale.com>
+ *          Grant Likely <grant.likely@secretlab.ca>
+ *
+ * Copyright (c) 2007 Freescale Semiconductor, Inc.
+ * Copyright (c) 2008 Secret Lab Technologies Ltd.
+ */
+
+#include "ops.h"
+#include "types.h"
+#include "io.h"
+#include "stdio.h"
+#include <libfdt.h>
+
+BSS_STACK(4*1024);
+
+extern int platform_specific_init(void) __attribute__((weak));
+
+void platform_init(unsigned long r3, unsigned long r4, unsigned long r5,
+		   unsigned long r6, unsigned long r7)
+{
+	const u32 *na, *ns, *reg, *timebase;
+	u64 memsize64;
+	int node, size, i;
+
+	/* Make sure FDT blob is sane */
+	if (fdt_check_header(_dtb_start) != 0)
+		fatal("Invalid device tree blob\n");
+
+	/* Find the #address-cells and #size-cells properties */
+	node = fdt_path_offset(_dtb_start, "/");
+	if (node < 0)
+		fatal("Cannot find root node\n");
+	na = fdt_getprop(_dtb_start, node, "#address-cells", &size);
+	if (!na || (size != 4))
+		fatal("Cannot find #address-cells property");
+	ns = fdt_getprop(_dtb_start, node, "#size-cells", &size);
+	if (!ns || (size != 4))
+		fatal("Cannot find #size-cells property");
+
+	/* Find the memory range */
+	node = fdt_node_offset_by_prop_value(_dtb_start, -1, "device_type",
+					     "memory", sizeof("memory"));
+	if (node < 0)
+		fatal("Cannot find memory node\n");
+	reg = fdt_getprop(_dtb_start, node, "reg", &size);
+	if (size < (*na+*ns) * sizeof(u32))
+		fatal("cannot get memory range\n");
+
+	/* Only interested in memory based at 0 */
+	for (i = 0; i < *na; i++)
+		if (*reg++ != 0)
+			fatal("Memory range is not based at address 0\n");
+
+	/* get the memsize and truncate it to under 4G on 32 bit machines */
+	memsize64 = 0;
+	for (i = 0; i < *ns; i++)
+		memsize64 = (memsize64 << 32) | *reg++;
+	if (sizeof(void *) == 4 && memsize64 >= 0x100000000ULL)
+		memsize64 = 0xffffffff;
+
+	/* finally, setup the timebase */
+	node = fdt_node_offset_by_prop_value(_dtb_start, -1, "device_type",
+					     "cpu", sizeof("cpu"));
+	if (node < 0)
+		fatal("Cannot find cpu node\n");
+	timebase = fdt_getprop(_dtb_start, node, "timebase-frequency", &size);
+	if (timebase && (size == 4))
+		timebase_period_ns = 1000000000 / *timebase;
+
+	/* Now we have the memory size; initialize the heap */
+	simple_alloc_init(_end, memsize64 - (unsigned long)_end, 32, 64);
+
+	/* prepare the device tree and find the console */
+	fdt_init(_dtb_start);
+
+	if (platform_specific_init)
+		platform_specific_init();
+
+	serial_console_init();
+}