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, 102 insertions, 0 deletions

diff --git a/drivers/net/phy/bcm63xx.c b/drivers/net/phy/bcm63xx.c
new file mode 100644
index 000000000..b46a736a3
--- /dev/null
+++ b/drivers/net/phy/bcm63xx.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *	Driver for Broadcom 63xx SOCs integrated PHYs
+ */
+#include "bcm-phy-lib.h"
+#include <linux/module.h>
+#include <linux/phy.h>
+
+#define MII_BCM63XX_IR		0x1a	/* interrupt register */
+#define MII_BCM63XX_IR_EN	0x4000	/* global interrupt enable */
+#define MII_BCM63XX_IR_DUPLEX	0x0800	/* duplex changed */
+#define MII_BCM63XX_IR_SPEED	0x0400	/* speed changed */
+#define MII_BCM63XX_IR_LINK	0x0200	/* link changed */
+#define MII_BCM63XX_IR_GMASK	0x0100	/* global interrupt mask */
+
+MODULE_DESCRIPTION("Broadcom 63xx internal PHY driver");
+MODULE_AUTHOR("Maxime Bizon <mbizon@freebox.fr>");
+MODULE_LICENSE("GPL");
+
+static int bcm63xx_config_intr(struct phy_device *phydev)
+{
+	int reg, err;
+
+	reg = phy_read(phydev, MII_BCM63XX_IR);
+	if (reg < 0)
+		return reg;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		err = bcm_phy_ack_intr(phydev);
+		if (err)
+			return err;
+
+		reg &= ~MII_BCM63XX_IR_GMASK;
+		err = phy_write(phydev, MII_BCM63XX_IR, reg);
+	} else {
+		reg |= MII_BCM63XX_IR_GMASK;
+		err = phy_write(phydev, MII_BCM63XX_IR, reg);
+		if (err)
+			return err;
+
+		err = bcm_phy_ack_intr(phydev);
+	}
+
+	return err;
+}
+
+static int bcm63xx_config_init(struct phy_device *phydev)
+{
+	int reg, err;
+
+	/* ASYM_PAUSE bit is marked RO in datasheet, so don't cheat */
+	linkmode_set_bit(ETHTOOL_LINK_MODE_Pause_BIT, phydev->supported);
+
+	reg = phy_read(phydev, MII_BCM63XX_IR);
+	if (reg < 0)
+		return reg;
+
+	/* Mask interrupts globally.  */
+	reg |= MII_BCM63XX_IR_GMASK;
+	err = phy_write(phydev, MII_BCM63XX_IR, reg);
+	if (err < 0)
+		return err;
+
+	/* Unmask events we are interested in  */
+	reg = ~(MII_BCM63XX_IR_DUPLEX |
+		MII_BCM63XX_IR_SPEED |
+		MII_BCM63XX_IR_LINK) |
+		MII_BCM63XX_IR_EN;
+	return phy_write(phydev, MII_BCM63XX_IR, reg);
+}
+
+static struct phy_driver bcm63xx_driver[] = {
+{
+	.phy_id		= 0x00406000,
+	.phy_id_mask	= 0xfffffc00,
+	.name		= "Broadcom BCM63XX (1)",
+	/* PHY_BASIC_FEATURES */
+	.flags		= PHY_IS_INTERNAL,
+	.config_init	= bcm63xx_config_init,
+	.config_intr	= bcm63xx_config_intr,
+	.handle_interrupt = bcm_phy_handle_interrupt,
+}, {
+	/* same phy as above, with just a different OUI */
+	.phy_id		= 0x002bdc00,
+	.phy_id_mask	= 0xfffffc00,
+	.name		= "Broadcom BCM63XX (2)",
+	/* PHY_BASIC_FEATURES */
+	.flags		= PHY_IS_INTERNAL,
+	.config_init	= bcm63xx_config_init,
+	.config_intr	= bcm63xx_config_intr,
+	.handle_interrupt = bcm_phy_handle_interrupt,
+} };
+
+module_phy_driver(bcm63xx_driver);
+
+static const struct mdio_device_id __maybe_unused bcm63xx_tbl[] = {
+	{ 0x00406000, 0xfffffc00 },
+	{ 0x002bdc00, 0xfffffc00 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(mdio, bcm63xx_tbl);