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, 137 insertions, 0 deletions

diff --git a/drivers/net/phy/ste10Xp.c b/drivers/net/phy/ste10Xp.c
new file mode 100644
index 000000000..d4835d4c5
--- /dev/null
+++ b/drivers/net/phy/ste10Xp.c
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * drivers/net/phy/ste10Xp.c
+ *
+ * Driver for STMicroelectronics STe10Xp PHYs
+ *
+ * Author: Giuseppe Cavallaro <peppe.cavallaro@st.com>
+ *
+ * Copyright (c) 2008 STMicroelectronics Limited
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/moduleparam.h>
+#include <linux/interrupt.h>
+#include <linux/netdevice.h>
+#include <linux/ethtool.h>
+#include <linux/mii.h>
+#include <linux/phy.h>
+
+#define MII_XCIIS	0x11	/* Configuration Info IRQ & Status Reg */
+#define MII_XIE		0x12	/* Interrupt Enable Register */
+#define MII_XIE_DEFAULT_MASK 0x0070 /* ANE complete, Remote Fault, Link Down */
+
+#define STE101P_PHY_ID		0x00061c50
+#define STE100P_PHY_ID		0x1c040011
+
+static int ste10Xp_config_init(struct phy_device *phydev)
+{
+	int value, err;
+
+	/* Software Reset PHY */
+	value = phy_read(phydev, MII_BMCR);
+	if (value < 0)
+		return value;
+
+	value |= BMCR_RESET;
+	err = phy_write(phydev, MII_BMCR, value);
+	if (err < 0)
+		return err;
+
+	do {
+		value = phy_read(phydev, MII_BMCR);
+	} while (value & BMCR_RESET);
+
+	return 0;
+}
+
+static int ste10Xp_ack_interrupt(struct phy_device *phydev)
+{
+	int err = phy_read(phydev, MII_XCIIS);
+
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static int ste10Xp_config_intr(struct phy_device *phydev)
+{
+	int err;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		/* clear any pending interrupts */
+		err = ste10Xp_ack_interrupt(phydev);
+		if (err)
+			return err;
+
+		/* Enable all STe101P interrupts (PR12) */
+		err = phy_write(phydev, MII_XIE, MII_XIE_DEFAULT_MASK);
+	} else {
+		err = phy_write(phydev, MII_XIE, 0);
+		if (err)
+			return err;
+
+		err = ste10Xp_ack_interrupt(phydev);
+	}
+
+	return err;
+}
+
+static irqreturn_t ste10Xp_handle_interrupt(struct phy_device *phydev)
+{
+	int irq_status;
+
+	irq_status = phy_read(phydev, MII_XCIIS);
+	if (irq_status < 0) {
+		phy_error(phydev);
+		return IRQ_NONE;
+	}
+
+	if (!(irq_status & MII_XIE_DEFAULT_MASK))
+		return IRQ_NONE;
+
+	phy_trigger_machine(phydev);
+
+	return IRQ_HANDLED;
+}
+
+static struct phy_driver ste10xp_pdriver[] = {
+{
+	.phy_id = STE101P_PHY_ID,
+	.phy_id_mask = 0xfffffff0,
+	.name = "STe101p",
+	/* PHY_BASIC_FEATURES */
+	.config_init = ste10Xp_config_init,
+	.config_intr = ste10Xp_config_intr,
+	.handle_interrupt = ste10Xp_handle_interrupt,
+	.suspend = genphy_suspend,
+	.resume = genphy_resume,
+}, {
+	.phy_id = STE100P_PHY_ID,
+	.phy_id_mask = 0xffffffff,
+	.name = "STe100p",
+	/* PHY_BASIC_FEATURES */
+	.config_init = ste10Xp_config_init,
+	.config_intr = ste10Xp_config_intr,
+	.handle_interrupt = ste10Xp_handle_interrupt,
+	.suspend = genphy_suspend,
+	.resume = genphy_resume,
+} };
+
+module_phy_driver(ste10xp_pdriver);
+
+static const struct mdio_device_id __maybe_unused ste10Xp_tbl[] = {
+	{ STE101P_PHY_ID, 0xfffffff0 },
+	{ STE100P_PHY_ID, 0xffffffff },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(mdio, ste10Xp_tbl);
+
+MODULE_DESCRIPTION("STMicroelectronics STe10Xp PHY driver");
+MODULE_AUTHOR("Giuseppe Cavallaro <peppe.cavallaro@st.com>");
+MODULE_LICENSE("GPL");