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, 287 insertions, 0 deletions

diff --git a/drivers/acpi/sbshc.c b/drivers/acpi/sbshc.c
new file mode 100644
index 000000000..c0ffa267f
--- /dev/null
+++ b/drivers/acpi/sbshc.c
@@ -0,0 +1,287 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * SMBus driver for ACPI Embedded Controller (v0.1)
+ *
+ * Copyright (c) 2007 Alexey Starikovskiy
+ */
+
+#define pr_fmt(fmt) "ACPI: " fmt
+
+#include <linux/acpi.h>
+#include <linux/wait.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+
+#include "sbshc.h"
+#include "internal.h"
+
+struct acpi_smb_hc {
+	struct acpi_ec *ec;
+	struct mutex lock;
+	wait_queue_head_t wait;
+	u8 offset;
+	u8 query_bit;
+	smbus_alarm_callback callback;
+	void *context;
+	bool done;
+};
+
+static int acpi_smbus_hc_probe(struct platform_device *pdev);
+static void acpi_smbus_hc_remove(struct platform_device *pdev);
+
+static const struct acpi_device_id sbs_device_ids[] = {
+	{"ACPI0001", 0},
+	{"ACPI0005", 0},
+	{"", 0},
+};
+
+MODULE_DEVICE_TABLE(acpi, sbs_device_ids);
+
+static struct platform_driver acpi_smb_hc_driver = {
+	.probe = acpi_smbus_hc_probe,
+	.remove = acpi_smbus_hc_remove,
+	.driver = {
+		.name = "acpi-smbus-hc",
+		.acpi_match_table = sbs_device_ids,
+	},
+};
+
+union acpi_smb_status {
+	u8 raw;
+	struct {
+		u8 status:5;
+		u8 reserved:1;
+		u8 alarm:1;
+		u8 done:1;
+	} fields;
+};
+
+enum acpi_smb_status_codes {
+	SMBUS_OK = 0,
+	SMBUS_UNKNOWN_FAILURE = 0x07,
+	SMBUS_DEVICE_ADDRESS_NACK = 0x10,
+	SMBUS_DEVICE_ERROR = 0x11,
+	SMBUS_DEVICE_COMMAND_ACCESS_DENIED = 0x12,
+	SMBUS_UNKNOWN_ERROR = 0x13,
+	SMBUS_DEVICE_ACCESS_DENIED = 0x17,
+	SMBUS_TIMEOUT = 0x18,
+	SMBUS_HOST_UNSUPPORTED_PROTOCOL = 0x19,
+	SMBUS_BUSY = 0x1a,
+	SMBUS_PEC_ERROR = 0x1f,
+};
+
+enum acpi_smb_offset {
+	ACPI_SMB_PROTOCOL = 0,	/* protocol, PEC */
+	ACPI_SMB_STATUS = 1,	/* status */
+	ACPI_SMB_ADDRESS = 2,	/* address */
+	ACPI_SMB_COMMAND = 3,	/* command */
+	ACPI_SMB_DATA = 4,	/* 32 data registers */
+	ACPI_SMB_BLOCK_COUNT = 0x24,	/* number of data bytes */
+	ACPI_SMB_ALARM_ADDRESS = 0x25,	/* alarm address */
+	ACPI_SMB_ALARM_DATA = 0x26,	/* 2 bytes alarm data */
+};
+
+static inline int smb_hc_read(struct acpi_smb_hc *hc, u8 address, u8 *data)
+{
+	return ec_read(hc->offset + address, data);
+}
+
+static inline int smb_hc_write(struct acpi_smb_hc *hc, u8 address, u8 data)
+{
+	return ec_write(hc->offset + address, data);
+}
+
+static int wait_transaction_complete(struct acpi_smb_hc *hc, int timeout)
+{
+	if (wait_event_timeout(hc->wait, hc->done, msecs_to_jiffies(timeout)))
+		return 0;
+	return -ETIME;
+}
+
+static int acpi_smbus_transaction(struct acpi_smb_hc *hc, u8 protocol,
+				  u8 address, u8 command, u8 *data, u8 length)
+{
+	int ret = -EFAULT, i;
+	u8 temp, sz = 0;
+
+	if (!hc) {
+		pr_err("host controller is not configured\n");
+		return ret;
+	}
+
+	mutex_lock(&hc->lock);
+	hc->done = false;
+	if (smb_hc_read(hc, ACPI_SMB_PROTOCOL, &temp))
+		goto end;
+	if (temp) {
+		ret = -EBUSY;
+		goto end;
+	}
+	smb_hc_write(hc, ACPI_SMB_COMMAND, command);
+	if (!(protocol & 0x01)) {
+		smb_hc_write(hc, ACPI_SMB_BLOCK_COUNT, length);
+		for (i = 0; i < length; ++i)
+			smb_hc_write(hc, ACPI_SMB_DATA + i, data[i]);
+	}
+	smb_hc_write(hc, ACPI_SMB_ADDRESS, address << 1);
+	smb_hc_write(hc, ACPI_SMB_PROTOCOL, protocol);
+	/*
+	 * Wait for completion. Save the status code, data size,
+	 * and data into the return package (if required by the protocol).
+	 */
+	ret = wait_transaction_complete(hc, 1000);
+	if (ret || !(protocol & 0x01))
+		goto end;
+	switch (protocol) {
+	case SMBUS_RECEIVE_BYTE:
+	case SMBUS_READ_BYTE:
+		sz = 1;
+		break;
+	case SMBUS_READ_WORD:
+		sz = 2;
+		break;
+	case SMBUS_READ_BLOCK:
+		if (smb_hc_read(hc, ACPI_SMB_BLOCK_COUNT, &sz)) {
+			ret = -EFAULT;
+			goto end;
+		}
+		sz &= 0x1f;
+		break;
+	}
+	for (i = 0; i < sz; ++i)
+		smb_hc_read(hc, ACPI_SMB_DATA + i, &data[i]);
+      end:
+	mutex_unlock(&hc->lock);
+	return ret;
+}
+
+int acpi_smbus_read(struct acpi_smb_hc *hc, u8 protocol, u8 address,
+		    u8 command, u8 *data)
+{
+	return acpi_smbus_transaction(hc, protocol, address, command, data, 0);
+}
+
+EXPORT_SYMBOL_GPL(acpi_smbus_read);
+
+int acpi_smbus_write(struct acpi_smb_hc *hc, u8 protocol, u8 address,
+		     u8 command, u8 *data, u8 length)
+{
+	return acpi_smbus_transaction(hc, protocol, address, command, data, length);
+}
+
+EXPORT_SYMBOL_GPL(acpi_smbus_write);
+
+int acpi_smbus_register_callback(struct acpi_smb_hc *hc,
+				 smbus_alarm_callback callback, void *context)
+{
+	mutex_lock(&hc->lock);
+	hc->callback = callback;
+	hc->context = context;
+	mutex_unlock(&hc->lock);
+	return 0;
+}
+
+EXPORT_SYMBOL_GPL(acpi_smbus_register_callback);
+
+int acpi_smbus_unregister_callback(struct acpi_smb_hc *hc)
+{
+	mutex_lock(&hc->lock);
+	hc->callback = NULL;
+	hc->context = NULL;
+	mutex_unlock(&hc->lock);
+	acpi_os_wait_events_complete();
+	return 0;
+}
+
+EXPORT_SYMBOL_GPL(acpi_smbus_unregister_callback);
+
+static inline void acpi_smbus_callback(void *context)
+{
+	struct acpi_smb_hc *hc = context;
+	if (hc->callback)
+		hc->callback(hc->context);
+}
+
+static int smbus_alarm(void *context)
+{
+	struct acpi_smb_hc *hc = context;
+	union acpi_smb_status status;
+	u8 address;
+	if (smb_hc_read(hc, ACPI_SMB_STATUS, &status.raw))
+		return 0;
+	/* Check if it is only a completion notify */
+	if (status.fields.done && status.fields.status == SMBUS_OK) {
+		hc->done = true;
+		wake_up(&hc->wait);
+	}
+	if (!status.fields.alarm)
+		return 0;
+	mutex_lock(&hc->lock);
+	smb_hc_read(hc, ACPI_SMB_ALARM_ADDRESS, &address);
+	status.fields.alarm = 0;
+	smb_hc_write(hc, ACPI_SMB_STATUS, status.raw);
+	/* We are only interested in events coming from known devices */
+	switch (address >> 1) {
+		case ACPI_SBS_CHARGER:
+		case ACPI_SBS_MANAGER:
+		case ACPI_SBS_BATTERY:
+			acpi_os_execute(OSL_NOTIFY_HANDLER,
+					acpi_smbus_callback, hc);
+	}
+	mutex_unlock(&hc->lock);
+	return 0;
+}
+
+static int acpi_smbus_hc_probe(struct platform_device *pdev)
+{
+	struct acpi_device *device;
+	int status;
+	unsigned long long val;
+	struct acpi_smb_hc *hc;
+
+	device = ACPI_COMPANION(&pdev->dev);
+	if (!device)
+		return -ENODEV;
+
+	status = acpi_evaluate_integer(device->handle, "_EC", NULL, &val);
+	if (ACPI_FAILURE(status)) {
+		pr_err("error obtaining _EC.\n");
+		return -EIO;
+	}
+
+	hc = kzalloc_obj(struct acpi_smb_hc);
+	if (!hc)
+		return -ENOMEM;
+	mutex_init(&hc->lock);
+	init_waitqueue_head(&hc->wait);
+
+	platform_set_drvdata(pdev, hc);
+
+	hc->ec = dev_get_drvdata(pdev->dev.parent);
+	hc->offset = (val >> 8) & 0xff;
+	hc->query_bit = val & 0xff;
+
+	acpi_ec_add_query_handler(hc->ec, hc->query_bit, NULL, smbus_alarm, hc);
+	dev_info(&device->dev, "SBS HC: offset = 0x%0x, query_bit = 0x%0x\n",
+		 hc->offset, hc->query_bit);
+
+	return 0;
+}
+
+static void acpi_smbus_hc_remove(struct platform_device *pdev)
+{
+	struct acpi_smb_hc *hc = platform_get_drvdata(pdev);
+
+	acpi_ec_remove_query_handler(hc->ec, hc->query_bit);
+	acpi_os_wait_events_complete();
+	kfree(hc);
+}
+
+module_platform_driver(acpi_smb_hc_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Alexey Starikovskiy");
+MODULE_DESCRIPTION("ACPI SMBus HC driver");