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, 154 insertions, 0 deletions

diff --git a/drivers/net/phy/cicada.c b/drivers/net/phy/cicada.c
new file mode 100644
index 000000000..d87cf8b94
--- /dev/null
+++ b/drivers/net/phy/cicada.c
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * drivers/net/phy/cicada.c
+ *
+ * Driver for Cicada PHYs
+ *
+ * Author: Andy Fleming
+ *
+ * Copyright (c) 2004 Freescale Semiconductor, Inc.
+ */
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/unistd.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/skbuff.h>
+#include <linux/spinlock.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mii.h>
+#include <linux/ethtool.h>
+#include <linux/phy.h>
+
+#include <linux/io.h>
+#include <asm/irq.h>
+#include <linux/uaccess.h>
+
+/* Cicada Extended Control Register 1 */
+#define MII_CIS8201_EXT_CON1           0x17
+#define MII_CIS8201_EXTCON1_INIT       0x0000
+
+/* Cicada Interrupt Mask Register */
+#define MII_CIS8201_IMASK		0x19
+#define MII_CIS8201_IMASK_IEN		0x8000
+#define MII_CIS8201_IMASK_SPEED	0x4000
+#define MII_CIS8201_IMASK_LINK		0x2000
+#define MII_CIS8201_IMASK_DUPLEX	0x1000
+#define MII_CIS8201_IMASK_MASK		0xf000
+
+/* Cicada Interrupt Status Register */
+#define MII_CIS8201_ISTAT		0x1a
+#define MII_CIS8201_ISTAT_STATUS	0x8000
+#define MII_CIS8201_ISTAT_SPEED	0x4000
+#define MII_CIS8201_ISTAT_LINK		0x2000
+#define MII_CIS8201_ISTAT_DUPLEX	0x1000
+
+/* Cicada Auxiliary Control/Status Register */
+#define MII_CIS8201_AUX_CONSTAT        0x1c
+#define MII_CIS8201_AUXCONSTAT_INIT    0x0004
+#define MII_CIS8201_AUXCONSTAT_DUPLEX  0x0020
+#define MII_CIS8201_AUXCONSTAT_SPEED   0x0018
+#define MII_CIS8201_AUXCONSTAT_GBIT    0x0010
+#define MII_CIS8201_AUXCONSTAT_100     0x0008
+
+MODULE_DESCRIPTION("Cicadia PHY driver");
+MODULE_AUTHOR("Andy Fleming");
+MODULE_LICENSE("GPL");
+
+static int cis820x_config_init(struct phy_device *phydev)
+{
+	int err;
+
+	err = phy_write(phydev, MII_CIS8201_AUX_CONSTAT,
+			MII_CIS8201_AUXCONSTAT_INIT);
+
+	if (err < 0)
+		return err;
+
+	err = phy_write(phydev, MII_CIS8201_EXT_CON1,
+			MII_CIS8201_EXTCON1_INIT);
+
+	return err;
+}
+
+static int cis820x_ack_interrupt(struct phy_device *phydev)
+{
+	int err = phy_read(phydev, MII_CIS8201_ISTAT);
+
+	return (err < 0) ? err : 0;
+}
+
+static int cis820x_config_intr(struct phy_device *phydev)
+{
+	int err;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		err = cis820x_ack_interrupt(phydev);
+		if (err)
+			return err;
+
+		err = phy_write(phydev, MII_CIS8201_IMASK,
+				MII_CIS8201_IMASK_MASK);
+	} else {
+		err = phy_write(phydev, MII_CIS8201_IMASK, 0);
+		if (err)
+			return err;
+
+		err = cis820x_ack_interrupt(phydev);
+	}
+
+	return err;
+}
+
+static irqreturn_t cis820x_handle_interrupt(struct phy_device *phydev)
+{
+	int irq_status;
+
+	irq_status = phy_read(phydev, MII_CIS8201_ISTAT);
+	if (irq_status < 0) {
+		phy_error(phydev);
+		return IRQ_NONE;
+	}
+
+	if (!(irq_status & MII_CIS8201_IMASK_MASK))
+		return IRQ_NONE;
+
+	phy_trigger_machine(phydev);
+
+	return IRQ_HANDLED;
+}
+
+/* Cicada 8201, a.k.a Vitesse VSC8201 */
+static struct phy_driver cis820x_driver[] = {
+{
+	.phy_id		= 0x000fc410,
+	.name		= "Cicada Cis8201",
+	.phy_id_mask	= 0x000ffff0,
+	/* PHY_GBIT_FEATURES */
+	.config_init	= &cis820x_config_init,
+	.config_intr	= &cis820x_config_intr,
+	.handle_interrupt = &cis820x_handle_interrupt,
+}, {
+	.phy_id		= 0x000fc440,
+	.name		= "Cicada Cis8204",
+	.phy_id_mask	= 0x000fffc0,
+	/* PHY_GBIT_FEATURES */
+	.config_init	= &cis820x_config_init,
+	.config_intr	= &cis820x_config_intr,
+	.handle_interrupt = &cis820x_handle_interrupt,
+} };
+
+module_phy_driver(cis820x_driver);
+
+static const struct mdio_device_id __maybe_unused cicada_tbl[] = {
+	{ 0x000fc410, 0x000ffff0 },
+	{ 0x000fc440, 0x000fffc0 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(mdio, cicada_tbl);