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, 82 insertions, 0 deletions

diff --git a/drivers/macintosh/macio_sysfs.c b/drivers/macintosh/macio_sysfs.c
new file mode 100644
index 000000000..2bbe359b2
--- /dev/null
+++ b/drivers/macintosh/macio_sysfs.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/stat.h>
+#include <asm/macio.h>
+
+static ssize_t
+compatible_show (struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct platform_device *of;
+	const char *compat;
+	int cplen;
+	int length = 0;
+
+	of = &to_macio_device (dev)->ofdev;
+	compat = of_get_property(of->dev.of_node, "compatible", &cplen);
+	if (!compat) {
+		*buf = '\0';
+		return 0;
+	}
+	while (cplen > 0) {
+		int l;
+		length += sprintf (buf, "%s\n", compat);
+		buf += length;
+		l = strlen (compat) + 1;
+		compat += l;
+		cplen -= l;
+	}
+
+	return length;
+}
+static DEVICE_ATTR_RO(compatible);
+
+static ssize_t modalias_show (struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	return of_device_modalias(dev, buf, PAGE_SIZE);
+}
+
+static ssize_t devspec_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct platform_device *ofdev;
+
+	ofdev = to_platform_device(dev);
+	return sprintf(buf, "%pOF\n", ofdev->dev.of_node);
+}
+static DEVICE_ATTR_RO(modalias);
+static DEVICE_ATTR_RO(devspec);
+
+static ssize_t name_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%pOFn\n", dev->of_node);
+}
+static DEVICE_ATTR_RO(name);
+
+static ssize_t type_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s\n", of_node_get_device_type(dev->of_node));
+}
+static DEVICE_ATTR_RO(type);
+
+static struct attribute *macio_dev_attrs[] = {
+	&dev_attr_name.attr,
+	&dev_attr_type.attr,
+	&dev_attr_compatible.attr,
+	&dev_attr_modalias.attr,
+	&dev_attr_devspec.attr,
+	NULL,
+};
+
+static const struct attribute_group macio_dev_group = {
+	.attrs = macio_dev_attrs,
+};
+
+const struct attribute_group *macio_dev_groups[] = {
+	&macio_dev_group,
+	NULL,
+};