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, 195 insertions, 0 deletions

diff --git a/drivers/misc/mei/debugfs.c b/drivers/misc/mei/debugfs.c
new file mode 100644
index 000000000..3b098d4c8
--- /dev/null
+++ b/drivers/misc/mei/debugfs.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2012-2022, Intel Corporation. All rights reserved
+ * Intel Management Engine Interface (Intel MEI) Linux driver
+ */
+
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+
+#include <linux/mei.h>
+
+#include "mei_dev.h"
+#include "client.h"
+#include "hw.h"
+
+static int mei_dbgfs_meclients_show(struct seq_file *m, void *unused)
+{
+	struct mei_device *dev = m->private;
+	struct mei_me_client *me_cl;
+	int i = 0;
+
+	if (!dev)
+		return -ENODEV;
+
+	down_read(&dev->me_clients_rwsem);
+
+	seq_puts(m, "  |id|fix|         UUID                       |con|msg len|sb|refc|vt|\n");
+
+	/*  if the driver is not enabled the list won't be consistent */
+	if (dev->dev_state != MEI_DEV_ENABLED)
+		goto out;
+
+	list_for_each_entry(me_cl, &dev->me_clients, list) {
+		if (!mei_me_cl_get(me_cl))
+			continue;
+
+		seq_printf(m, "%2d|%2d|%3d|%pUl|%3d|%7d|%2d|%4d|%2d|\n",
+			   i++, me_cl->client_id,
+			   me_cl->props.fixed_address,
+			   &me_cl->props.protocol_name,
+			   me_cl->props.max_number_of_connections,
+			   me_cl->props.max_msg_length,
+			   me_cl->props.single_recv_buf,
+			   kref_read(&me_cl->refcnt),
+			   me_cl->props.vt_supported);
+		mei_me_cl_put(me_cl);
+	}
+
+out:
+	up_read(&dev->me_clients_rwsem);
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(mei_dbgfs_meclients);
+
+static int mei_dbgfs_active_show(struct seq_file *m, void *unused)
+{
+	struct mei_device *dev = m->private;
+	struct mei_cl *cl;
+	int i = 0;
+
+	if (!dev)
+		return -ENODEV;
+
+	mutex_lock(&dev->device_lock);
+
+	seq_puts(m, "   |me|host|state|rd|wr|wrq\n");
+
+	/*  if the driver is not enabled the list won't be consistent */
+	if (dev->dev_state != MEI_DEV_ENABLED)
+		goto out;
+
+	list_for_each_entry(cl, &dev->file_list, link) {
+
+		seq_printf(m, "%3d|%2d|%4d|%5d|%2d|%2d|%3u\n",
+			   i, mei_cl_me_id(cl), cl->host_client_id, cl->state,
+			   !list_empty(&cl->rd_completed), cl->writing_state,
+			   cl->tx_cb_queued);
+		i++;
+	}
+out:
+	mutex_unlock(&dev->device_lock);
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(mei_dbgfs_active);
+
+static const char *mei_dev_pxp_mode_str(enum mei_dev_pxp_mode state)
+{
+#define MEI_PXP_MODE(state) case MEI_DEV_PXP_##state: return #state
+	switch (state) {
+	MEI_PXP_MODE(DEFAULT);
+	MEI_PXP_MODE(INIT);
+	MEI_PXP_MODE(SETUP);
+	MEI_PXP_MODE(READY);
+	default:
+		return "unknown";
+	}
+#undef MEI_PXP_MODE
+}
+
+static int mei_dbgfs_devstate_show(struct seq_file *m, void *unused)
+{
+	struct mei_device *dev = m->private;
+
+	seq_printf(m, "dev: %s\n", mei_dev_state_str(dev->dev_state));
+	seq_printf(m, "hbm: %s\n", mei_hbm_state_str(dev->hbm_state));
+
+	if (dev->hbm_state >= MEI_HBM_ENUM_CLIENTS &&
+	    dev->hbm_state <= MEI_HBM_STARTED) {
+		seq_puts(m, "hbm features:\n");
+		seq_printf(m, "\tPG: %01d\n", dev->hbm_f_pg_supported);
+		seq_printf(m, "\tDC: %01d\n", dev->hbm_f_dc_supported);
+		seq_printf(m, "\tIE: %01d\n", dev->hbm_f_ie_supported);
+		seq_printf(m, "\tDOT: %01d\n", dev->hbm_f_dot_supported);
+		seq_printf(m, "\tEV: %01d\n", dev->hbm_f_ev_supported);
+		seq_printf(m, "\tFA: %01d\n", dev->hbm_f_fa_supported);
+		seq_printf(m, "\tOS: %01d\n", dev->hbm_f_os_supported);
+		seq_printf(m, "\tDR: %01d\n", dev->hbm_f_dr_supported);
+		seq_printf(m, "\tVT: %01d\n", dev->hbm_f_vt_supported);
+		seq_printf(m, "\tCAP: %01d\n", dev->hbm_f_cap_supported);
+		seq_printf(m, "\tCD: %01d\n", dev->hbm_f_cd_supported);
+	}
+
+	seq_printf(m, "pg:  %s, %s\n",
+		   mei_pg_is_enabled(dev) ? "ENABLED" : "DISABLED",
+		   mei_pg_state_str(mei_pg_state(dev)));
+
+	seq_printf(m, "pxp: %s\n", mei_dev_pxp_mode_str(dev->pxp_mode));
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(mei_dbgfs_devstate);
+
+static ssize_t mei_dbgfs_write_allow_fa(struct file *file,
+					const char __user *user_buf,
+					size_t count, loff_t *ppos)
+{
+	struct mei_device *dev;
+	int ret;
+
+	dev = container_of(file->private_data,
+			   struct mei_device, allow_fixed_address);
+
+	ret = debugfs_write_file_bool(file, user_buf, count, ppos);
+	if (ret < 0)
+		return ret;
+	dev->override_fixed_address = true;
+	return ret;
+}
+
+static const struct file_operations mei_dbgfs_allow_fa_fops = {
+	.open = simple_open,
+	.read = debugfs_read_file_bool,
+	.write = mei_dbgfs_write_allow_fa,
+	.llseek = generic_file_llseek,
+};
+
+/**
+ * mei_dbgfs_deregister - Remove the debugfs files and directories
+ *
+ * @dev: the mei device structure
+ */
+void mei_dbgfs_deregister(struct mei_device *dev)
+{
+	if (!dev->dbgfs_dir)
+		return;
+	debugfs_remove_recursive(dev->dbgfs_dir);
+	dev->dbgfs_dir = NULL;
+}
+
+/**
+ * mei_dbgfs_register - Add the debugfs files
+ *
+ * @dev: the mei device structure
+ * @name: the mei device name
+ */
+void mei_dbgfs_register(struct mei_device *dev, const char *name)
+{
+	struct dentry *dir;
+
+	dir = debugfs_create_dir(name, NULL);
+	dev->dbgfs_dir = dir;
+
+	debugfs_create_file("meclients", S_IRUSR, dir, dev,
+			    &mei_dbgfs_meclients_fops);
+	debugfs_create_file("active", S_IRUSR, dir, dev,
+			    &mei_dbgfs_active_fops);
+	debugfs_create_file("devstate", S_IRUSR, dir, dev,
+			    &mei_dbgfs_devstate_fops);
+	debugfs_create_file("allow_fixed_address", S_IRUSR | S_IWUSR, dir,
+			    &dev->allow_fixed_address,
+			    &mei_dbgfs_allow_fa_fops);
+}