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, 95 insertions, 0 deletions

diff --git a/sound/soc/sof/ipc4-telemetry.c b/sound/soc/sof/ipc4-telemetry.c
new file mode 100644
index 000000000..ddc3bc494
--- /dev/null
+++ b/sound/soc/sof/ipc4-telemetry.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+//
+// This file is provided under a dual BSD/GPLv2 license.  When using or
+// redistributing this file, you may do so under either license.
+//
+// Copyright(c) 2018-2023 Intel Corporation
+//
+
+#include <linux/debugfs.h>
+#include <linux/io.h>
+#include <linux/pm_runtime.h>
+#include <sound/sof/debug.h>
+#include <sound/sof/ipc4/header.h>
+#include "sof-priv.h"
+#include "ops.h"
+#include "ipc4-telemetry.h"
+#include "ipc4-priv.h"
+
+static void __iomem *sof_ipc4_query_exception_address(struct snd_sof_dev *sdev)
+{
+	u32 type = SOF_IPC4_DEBUG_SLOT_TELEMETRY;
+	size_t telemetry_slot_offset;
+	u32 offset;
+
+	telemetry_slot_offset = sof_ipc4_find_debug_slot_offset_by_type(sdev, type);
+	if (!telemetry_slot_offset)
+		return NULL;
+
+	/* skip the first separator magic number */
+	offset = telemetry_slot_offset + sizeof(u32);
+
+	return sdev->bar[sdev->mailbox_bar] + offset;
+}
+
+static ssize_t sof_telemetry_entry_read(struct file *file, char __user *buffer,
+					size_t count, loff_t *ppos)
+{
+	struct snd_sof_dfsentry *dfse = file->private_data;
+	struct snd_sof_dev *sdev = dfse->sdev;
+	void __iomem *io_addr;
+	loff_t pos = *ppos;
+	size_t size_ret;
+	u8 *buf;
+
+	if (pos < 0)
+		return -EINVAL;
+	/* skip the first separator magic number */
+	if (pos >= SOF_IPC4_DEBUG_SLOT_SIZE - 4 || !count)
+		return 0;
+	if (count > SOF_IPC4_DEBUG_SLOT_SIZE - 4 - pos)
+		count = SOF_IPC4_DEBUG_SLOT_SIZE - 4 - pos;
+
+	io_addr = sof_ipc4_query_exception_address(sdev);
+	if (!io_addr)
+		return -EFAULT;
+
+	buf = kzalloc(SOF_IPC4_DEBUG_SLOT_SIZE - 4, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	memcpy_fromio(buf, io_addr, SOF_IPC4_DEBUG_SLOT_SIZE - 4);
+	size_ret = copy_to_user(buffer, buf + pos, count);
+	if (size_ret) {
+		kfree(buf);
+		return -EFAULT;
+	}
+
+	*ppos = pos + count;
+	kfree(buf);
+
+	return count;
+}
+
+static const struct file_operations sof_telemetry_fops = {
+	.open = simple_open,
+	.read = sof_telemetry_entry_read,
+};
+
+void sof_ipc4_create_exception_debugfs_node(struct snd_sof_dev *sdev)
+{
+	struct snd_sof_dfsentry *dfse;
+
+	dfse = devm_kzalloc(sdev->dev, sizeof(*dfse), GFP_KERNEL);
+	if (!dfse)
+		return;
+
+	dfse->type = SOF_DFSENTRY_TYPE_IOMEM;
+	dfse->size = SOF_IPC4_DEBUG_SLOT_SIZE - 4;
+	dfse->access_type = SOF_DEBUGFS_ACCESS_ALWAYS;
+	dfse->sdev = sdev;
+
+	list_add(&dfse->list, &sdev->dfsentry_list);
+
+	debugfs_create_file("exception", 0444, sdev->debugfs_root, dfse, &sof_telemetry_fops);
+}