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, 256 insertions, 0 deletions

diff --git a/drivers/thunderbolt/cap.c b/drivers/thunderbolt/cap.c
new file mode 100644
index 000000000..4ab22d529
--- /dev/null
+++ b/drivers/thunderbolt/cap.c
@@ -0,0 +1,256 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Thunderbolt driver - capabilities lookup
+ *
+ * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
+ * Copyright (C) 2018, Intel Corporation
+ */
+
+#include <linux/slab.h>
+#include <linux/errno.h>
+
+#include "tb.h"
+
+#define CAP_OFFSET_MAX		0xff
+#define VSE_CAP_OFFSET_MAX	0xffff
+#define TMU_ACCESS_EN		BIT(20)
+
+static int tb_port_enable_tmu(struct tb_port *port, bool enable)
+{
+	struct tb_switch *sw = port->sw;
+	u32 value, offset;
+	int ret;
+
+	/*
+	 * Legacy devices need to have TMU access enabled before port
+	 * space can be fully accessed.
+	 */
+	if (tb_switch_is_light_ridge(sw))
+		offset = 0x26;
+	else if (tb_switch_is_eagle_ridge(sw))
+		offset = 0x2a;
+	else
+		return 0;
+
+	ret = tb_sw_read(sw, &value, TB_CFG_SWITCH, offset, 1);
+	if (ret)
+		return ret;
+
+	if (enable)
+		value |= TMU_ACCESS_EN;
+	else
+		value &= ~TMU_ACCESS_EN;
+
+	return tb_sw_write(sw, &value, TB_CFG_SWITCH, offset, 1);
+}
+
+static void tb_port_dummy_read(struct tb_port *port)
+{
+	/*
+	 * When reading from next capability pointer location in port
+	 * config space the read data is not cleared on LR. To avoid
+	 * reading stale data on next read perform one dummy read after
+	 * port capabilities are walked.
+	 */
+	if (tb_switch_is_light_ridge(port->sw)) {
+		u32 dummy;
+
+		tb_port_read(port, &dummy, TB_CFG_PORT, 0, 1);
+	}
+}
+
+/**
+ * tb_port_next_cap() - Return next capability in the linked list
+ * @port: Port to find the capability for
+ * @offset: Previous capability offset (%0 for start)
+ *
+ * Finds dword offset of the next capability in port config space
+ * capability list. When passed %0 in @offset parameter, first entry
+ * will be returned, if it exists.
+ *
+ * Return:
+ * * Double word offset of the first or next capability - On success.
+ * * %0 - If no next capability is found.
+ * * Negative errno - Another error occurred.
+ */
+int tb_port_next_cap(struct tb_port *port, unsigned int offset)
+{
+	struct tb_cap_any header;
+	int ret;
+
+	if (!offset)
+		return port->config.first_cap_offset;
+
+	ret = tb_port_read(port, &header, TB_CFG_PORT, offset, 1);
+	if (ret)
+		return ret;
+
+	return header.basic.next;
+}
+
+static int __tb_port_find_cap(struct tb_port *port, enum tb_port_cap cap)
+{
+	int offset = 0;
+
+	do {
+		struct tb_cap_any header;
+		int ret;
+
+		offset = tb_port_next_cap(port, offset);
+		if (offset < 0)
+			return offset;
+
+		ret = tb_port_read(port, &header, TB_CFG_PORT, offset, 1);
+		if (ret)
+			return ret;
+
+		if (header.basic.cap == cap)
+			return offset;
+	} while (offset > 0);
+
+	return -ENOENT;
+}
+
+/**
+ * tb_port_find_cap() - Find port capability
+ * @port: Port to find the capability for
+ * @cap: Capability to look
+ *
+ * Return:
+ * * Offset to the start of capability - On success.
+ * * %-ENOENT - If no such capability was found.
+ * * Negative errno - Another error occurred.
+ */
+int tb_port_find_cap(struct tb_port *port, enum tb_port_cap cap)
+{
+	int ret;
+
+	ret = tb_port_enable_tmu(port, true);
+	if (ret)
+		return ret;
+
+	ret = __tb_port_find_cap(port, cap);
+
+	tb_port_dummy_read(port);
+	tb_port_enable_tmu(port, false);
+
+	return ret;
+}
+
+/**
+ * tb_switch_next_cap() - Return next capability in the linked list
+ * @sw: Switch to find the capability for
+ * @offset: Previous capability offset (%0 for start)
+ *
+ * Finds dword offset of the next capability in port config space
+ * capability list. When passed %0 in @offset parameter, first entry
+ * will be returned, if it exists.
+ *
+ * Return:
+ * * Double word offset of the first or next capability - On success.
+ * * %0 - If no next capability is found.
+ * * Negative errno - Another error occurred.
+ */
+int tb_switch_next_cap(struct tb_switch *sw, unsigned int offset)
+{
+	struct tb_cap_any header;
+	int ret;
+
+	if (!offset)
+		return sw->config.first_cap_offset;
+
+	ret = tb_sw_read(sw, &header, TB_CFG_SWITCH, offset, 2);
+	if (ret)
+		return ret;
+
+	switch (header.basic.cap) {
+	case TB_SWITCH_CAP_TMU:
+		ret = header.basic.next;
+		break;
+
+	case TB_SWITCH_CAP_VSE:
+		if (!header.extended_short.length)
+			ret = header.extended_long.next;
+		else
+			ret = header.extended_short.next;
+		break;
+
+	default:
+		tb_sw_dbg(sw, "unknown capability %#x at %#x\n",
+			  header.basic.cap, offset);
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret >= VSE_CAP_OFFSET_MAX ? 0 : ret;
+}
+
+/**
+ * tb_switch_find_cap() - Find switch capability
+ * @sw: Switch to find the capability for
+ * @cap: Capability to look
+ *
+ * Return:
+ * * Offset to the start of capability - On success.
+ * * %-ENOENT - If no such capability was found.
+ * * Negative errno - Another error occurred.
+ */
+int tb_switch_find_cap(struct tb_switch *sw, enum tb_switch_cap cap)
+{
+	int offset = 0;
+
+	do {
+		struct tb_cap_any header;
+		int ret;
+
+		offset = tb_switch_next_cap(sw, offset);
+		if (offset < 0)
+			return offset;
+
+		ret = tb_sw_read(sw, &header, TB_CFG_SWITCH, offset, 1);
+		if (ret)
+			return ret;
+
+		if (header.basic.cap == cap)
+			return offset;
+	} while (offset);
+
+	return -ENOENT;
+}
+
+/**
+ * tb_switch_find_vse_cap() - Find switch vendor specific capability
+ * @sw: Switch to find the capability for
+ * @vsec: Vendor specific capability to look
+ *
+ * This function enumerates vendor specific capabilities (VSEC) of a
+ * switch and returns offset when capability matching @vsec is found.
+ *
+ * Return:
+ * * Offset of capability - On success.
+ * * %-ENOENT - If capability was not found.
+ * * Negative errno - Another error occurred.
+ */
+int tb_switch_find_vse_cap(struct tb_switch *sw, enum tb_switch_vse_cap vsec)
+{
+	int offset = 0;
+
+	do {
+		struct tb_cap_any header;
+		int ret;
+
+		offset = tb_switch_next_cap(sw, offset);
+		if (offset < 0)
+			return offset;
+
+		ret = tb_sw_read(sw, &header, TB_CFG_SWITCH, offset, 1);
+		if (ret)
+			return ret;
+
+		if (header.extended_short.cap == TB_SWITCH_CAP_VSE &&
+		    header.extended_short.vsec_id == vsec)
+			return offset;
+	} while (offset);
+
+	return -ENOENT;
+}