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, 98 insertions, 0 deletions

diff --git a/drivers/net/phy/uPD60620.c b/drivers/net/phy/uPD60620.c
new file mode 100644
index 000000000..900cb756c
--- /dev/null
+++ b/drivers/net/phy/uPD60620.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Driver for the Renesas PHY uPD60620.
+ *
+ * Copyright (C) 2015 Softing Industrial Automation GmbH
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/phy.h>
+
+#define UPD60620_PHY_ID    0xb8242824
+
+/* Extended Registers and values */
+/* PHY Special Control/Status    */
+#define PHY_PHYSCR         0x1F      /* PHY.31 */
+#define PHY_PHYSCR_10MB    0x0004    /* PHY speed = 10mb */
+#define PHY_PHYSCR_100MB   0x0008    /* PHY speed = 100mb */
+#define PHY_PHYSCR_DUPLEX  0x0010    /* PHY Duplex */
+
+/* PHY Special Modes */
+#define PHY_SPM            0x12      /* PHY.18 */
+
+/* Init PHY */
+
+static int upd60620_config_init(struct phy_device *phydev)
+{
+	/* Enable support for passive HUBs (could be a strap option) */
+	/* PHYMODE: All speeds, HD in parallel detect */
+	return phy_write(phydev, PHY_SPM, 0x0180 | phydev->mdio.addr);
+}
+
+/* Get PHY status from common registers */
+
+static int upd60620_read_status(struct phy_device *phydev)
+{
+	int phy_state;
+
+	/* Read negotiated state */
+	phy_state = phy_read(phydev, MII_BMSR);
+	if (phy_state < 0)
+		return phy_state;
+
+	phydev->link = 0;
+	linkmode_zero(phydev->lp_advertising);
+	phydev->pause = 0;
+	phydev->asym_pause = 0;
+
+	if (phy_state & (BMSR_ANEGCOMPLETE | BMSR_LSTATUS)) {
+		phy_state = phy_read(phydev, PHY_PHYSCR);
+		if (phy_state < 0)
+			return phy_state;
+
+		if (phy_state & (PHY_PHYSCR_10MB | PHY_PHYSCR_100MB)) {
+			phydev->link = 1;
+			phydev->speed = SPEED_10;
+			phydev->duplex = DUPLEX_HALF;
+
+			if (phy_state & PHY_PHYSCR_100MB)
+				phydev->speed = SPEED_100;
+			if (phy_state & PHY_PHYSCR_DUPLEX)
+				phydev->duplex = DUPLEX_FULL;
+
+			phy_state = phy_read(phydev, MII_LPA);
+			if (phy_state < 0)
+				return phy_state;
+
+			mii_lpa_to_linkmode_lpa_t(phydev->lp_advertising,
+						  phy_state);
+
+			phy_resolve_aneg_pause(phydev);
+		}
+	}
+	return 0;
+}
+
+MODULE_DESCRIPTION("Renesas uPD60620 PHY driver");
+MODULE_AUTHOR("Bernd Edlinger <bernd.edlinger@hotmail.de>");
+MODULE_LICENSE("GPL");
+
+static struct phy_driver upd60620_driver[1] = { {
+	.phy_id         = UPD60620_PHY_ID,
+	.phy_id_mask    = 0xfffffffe,
+	.name           = "Renesas uPD60620",
+	/* PHY_BASIC_FEATURES */
+	.flags          = 0,
+	.config_init    = upd60620_config_init,
+	.read_status    = upd60620_read_status,
+} };
+
+module_phy_driver(upd60620_driver);
+
+static const struct mdio_device_id __maybe_unused upd60620_tbl[] = {
+	{ UPD60620_PHY_ID, 0xfffffffe },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(mdio, upd60620_tbl);