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, 450 insertions, 0 deletions

diff --git a/net/ethtool/cabletest.c b/net/ethtool/cabletest.c
new file mode 100644
index 000000000..9c22d4c76
--- /dev/null
+++ b/net/ethtool/cabletest.c
@@ -0,0 +1,450 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/phy.h>
+#include <linux/ethtool_netlink.h>
+#include <net/netdev_lock.h>
+
+#include "common.h"
+#include "netlink.h"
+
+/* 802.3 standard allows 100 meters for BaseT cables. However longer
+ * cables might work, depending on the quality of the cables and the
+ * PHY. So allow testing for up to 150 meters.
+ */
+#define MAX_CABLE_LENGTH_CM (150 * 100)
+
+const struct nla_policy ethnl_cable_test_act_policy[] = {
+	[ETHTOOL_A_CABLE_TEST_HEADER]		=
+		NLA_POLICY_NESTED(ethnl_header_policy_phy),
+};
+
+static int ethnl_cable_test_started(struct phy_device *phydev, u8 cmd)
+{
+	struct sk_buff *skb;
+	int err = -ENOMEM;
+	void *ehdr;
+
+	skb = genlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+	if (!skb)
+		goto out;
+
+	ehdr = ethnl_bcastmsg_put(skb, cmd);
+	if (!ehdr) {
+		err = -EMSGSIZE;
+		goto out;
+	}
+
+	err = ethnl_fill_reply_header(skb, phydev->attached_dev,
+				      ETHTOOL_A_CABLE_TEST_NTF_HEADER);
+	if (err)
+		goto out;
+
+	err = nla_put_u8(skb, ETHTOOL_A_CABLE_TEST_NTF_STATUS,
+			 ETHTOOL_A_CABLE_TEST_NTF_STATUS_STARTED);
+	if (err)
+		goto out;
+
+	genlmsg_end(skb, ehdr);
+
+	return ethnl_multicast(skb, phydev->attached_dev);
+
+out:
+	nlmsg_free(skb);
+	phydev_err(phydev, "%s: Error %pe\n", __func__, ERR_PTR(err));
+
+	return err;
+}
+
+int ethnl_act_cable_test(struct sk_buff *skb, struct genl_info *info)
+{
+	struct ethnl_req_info req_info = {};
+	const struct ethtool_phy_ops *ops;
+	struct nlattr **tb = info->attrs;
+	struct phy_device *phydev;
+	struct net_device *dev;
+	int ret;
+
+	ret = ethnl_parse_header_dev_get(&req_info,
+					 tb[ETHTOOL_A_CABLE_TEST_HEADER],
+					 genl_info_net(info), info->extack,
+					 true);
+	if (ret < 0)
+		return ret;
+
+	dev = req_info.dev;
+
+	netdev_lock_ops_compat(dev);
+	phydev = ethnl_req_get_phydev(&req_info, tb,
+				      ETHTOOL_A_CABLE_TEST_HEADER,
+				      info->extack);
+	if (IS_ERR_OR_NULL(phydev)) {
+		ret = -EOPNOTSUPP;
+		goto out_unlock;
+	}
+
+	ops = ethtool_phy_ops;
+	if (!ops || !ops->start_cable_test) {
+		ret = -EOPNOTSUPP;
+		goto out_unlock;
+	}
+
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		goto out_unlock;
+
+	ret = ops->start_cable_test(phydev, info->extack);
+
+	ethnl_ops_complete(dev);
+
+	if (!ret)
+		ethnl_cable_test_started(phydev, ETHTOOL_MSG_CABLE_TEST_NTF);
+
+out_unlock:
+	netdev_unlock_ops_compat(dev);
+	ethnl_parse_header_dev_put(&req_info);
+	return ret;
+}
+
+int ethnl_cable_test_alloc(struct phy_device *phydev, u8 cmd)
+{
+	int err = -ENOMEM;
+
+	/* One TDR sample occupies 20 bytes. For a 150 meter cable,
+	 * with four pairs, around 12K is needed.
+	 */
+	phydev->skb = genlmsg_new(SZ_16K, GFP_KERNEL);
+	if (!phydev->skb)
+		goto out;
+
+	phydev->ehdr = ethnl_bcastmsg_put(phydev->skb, cmd);
+	if (!phydev->ehdr) {
+		err = -EMSGSIZE;
+		goto out;
+	}
+
+	err = ethnl_fill_reply_header(phydev->skb, phydev->attached_dev,
+				      ETHTOOL_A_CABLE_TEST_NTF_HEADER);
+	if (err)
+		goto out;
+
+	err = nla_put_u8(phydev->skb, ETHTOOL_A_CABLE_TEST_NTF_STATUS,
+			 ETHTOOL_A_CABLE_TEST_NTF_STATUS_COMPLETED);
+	if (err)
+		goto out;
+
+	phydev->nest = nla_nest_start(phydev->skb,
+				      ETHTOOL_A_CABLE_TEST_NTF_NEST);
+	if (!phydev->nest) {
+		err = -EMSGSIZE;
+		goto out;
+	}
+
+	return 0;
+
+out:
+	nlmsg_free(phydev->skb);
+	phydev->skb = NULL;
+	return err;
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_alloc);
+
+void ethnl_cable_test_free(struct phy_device *phydev)
+{
+	nlmsg_free(phydev->skb);
+	phydev->skb = NULL;
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_free);
+
+void ethnl_cable_test_finished(struct phy_device *phydev)
+{
+	nla_nest_end(phydev->skb, phydev->nest);
+
+	genlmsg_end(phydev->skb, phydev->ehdr);
+
+	ethnl_multicast(phydev->skb, phydev->attached_dev);
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_finished);
+
+int ethnl_cable_test_result_with_src(struct phy_device *phydev, u8 pair,
+				     u8 result, u32 src)
+{
+	struct nlattr *nest;
+	int ret = -EMSGSIZE;
+
+	nest = nla_nest_start(phydev->skb, ETHTOOL_A_CABLE_NEST_RESULT);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_u8(phydev->skb, ETHTOOL_A_CABLE_RESULT_PAIR, pair))
+		goto err;
+	if (nla_put_u8(phydev->skb, ETHTOOL_A_CABLE_RESULT_CODE, result))
+		goto err;
+	if (src != ETHTOOL_A_CABLE_INF_SRC_UNSPEC) {
+		if (nla_put_u32(phydev->skb, ETHTOOL_A_CABLE_RESULT_SRC, src))
+			goto err;
+	}
+
+	nla_nest_end(phydev->skb, nest);
+	return 0;
+
+err:
+	nla_nest_cancel(phydev->skb, nest);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_result_with_src);
+
+int ethnl_cable_test_fault_length_with_src(struct phy_device *phydev, u8 pair,
+					   u32 cm, u32 src)
+{
+	struct nlattr *nest;
+	int ret = -EMSGSIZE;
+
+	nest = nla_nest_start(phydev->skb,
+			      ETHTOOL_A_CABLE_NEST_FAULT_LENGTH);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_u8(phydev->skb, ETHTOOL_A_CABLE_FAULT_LENGTH_PAIR, pair))
+		goto err;
+	if (nla_put_u32(phydev->skb, ETHTOOL_A_CABLE_FAULT_LENGTH_CM, cm))
+		goto err;
+	if (src != ETHTOOL_A_CABLE_INF_SRC_UNSPEC) {
+		if (nla_put_u32(phydev->skb, ETHTOOL_A_CABLE_FAULT_LENGTH_SRC,
+				src))
+			goto err;
+	}
+
+	nla_nest_end(phydev->skb, nest);
+	return 0;
+
+err:
+	nla_nest_cancel(phydev->skb, nest);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_fault_length_with_src);
+
+static const struct nla_policy cable_test_tdr_act_cfg_policy[] = {
+	[ETHTOOL_A_CABLE_TEST_TDR_CFG_FIRST]	= { .type = NLA_U32 },
+	[ETHTOOL_A_CABLE_TEST_TDR_CFG_LAST]	= { .type = NLA_U32 },
+	[ETHTOOL_A_CABLE_TEST_TDR_CFG_STEP]	= { .type = NLA_U32 },
+	[ETHTOOL_A_CABLE_TEST_TDR_CFG_PAIR]	= { .type = NLA_U8 },
+};
+
+const struct nla_policy ethnl_cable_test_tdr_act_policy[] = {
+	[ETHTOOL_A_CABLE_TEST_TDR_HEADER]	=
+		NLA_POLICY_NESTED(ethnl_header_policy_phy),
+	[ETHTOOL_A_CABLE_TEST_TDR_CFG]		= { .type = NLA_NESTED },
+};
+
+/* CABLE_TEST_TDR_ACT */
+static int ethnl_act_cable_test_tdr_cfg(const struct nlattr *nest,
+					struct genl_info *info,
+					struct phy_tdr_config *cfg)
+{
+	struct nlattr *tb[ARRAY_SIZE(cable_test_tdr_act_cfg_policy)];
+	int ret;
+
+	cfg->first = 100;
+	cfg->step = 100;
+	cfg->last = MAX_CABLE_LENGTH_CM;
+	cfg->pair = PHY_PAIR_ALL;
+
+	if (!nest)
+		return 0;
+
+	ret = nla_parse_nested(tb,
+			       ARRAY_SIZE(cable_test_tdr_act_cfg_policy) - 1,
+			       nest, cable_test_tdr_act_cfg_policy,
+			       info->extack);
+	if (ret < 0)
+		return ret;
+
+	if (tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_FIRST])
+		cfg->first = nla_get_u32(
+			tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_FIRST]);
+
+	if (tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_LAST])
+		cfg->last = nla_get_u32(tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_LAST]);
+
+	if (tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_STEP])
+		cfg->step = nla_get_u32(tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_STEP]);
+
+	if (tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_PAIR]) {
+		cfg->pair = nla_get_u8(tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_PAIR]);
+		if (cfg->pair > ETHTOOL_A_CABLE_PAIR_D) {
+			NL_SET_ERR_MSG_ATTR(
+				info->extack,
+				tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_PAIR],
+				"invalid pair parameter");
+			return -EINVAL;
+		}
+	}
+
+	if (cfg->first > MAX_CABLE_LENGTH_CM) {
+		NL_SET_ERR_MSG_ATTR(info->extack,
+				    tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_FIRST],
+				    "invalid first parameter");
+		return -EINVAL;
+	}
+
+	if (cfg->last > MAX_CABLE_LENGTH_CM) {
+		NL_SET_ERR_MSG_ATTR(info->extack,
+				    tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_LAST],
+				    "invalid last parameter");
+		return -EINVAL;
+	}
+
+	if (cfg->first > cfg->last) {
+		NL_SET_ERR_MSG(info->extack, "invalid first/last parameter");
+		return -EINVAL;
+	}
+
+	if (!cfg->step) {
+		NL_SET_ERR_MSG_ATTR(info->extack,
+				    tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_STEP],
+				    "invalid step parameter");
+		return -EINVAL;
+	}
+
+	if (cfg->step > (cfg->last - cfg->first)) {
+		NL_SET_ERR_MSG_ATTR(info->extack,
+				    tb[ETHTOOL_A_CABLE_TEST_TDR_CFG_STEP],
+				    "step parameter too big");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int ethnl_act_cable_test_tdr(struct sk_buff *skb, struct genl_info *info)
+{
+	struct ethnl_req_info req_info = {};
+	const struct ethtool_phy_ops *ops;
+	struct nlattr **tb = info->attrs;
+	struct phy_device *phydev;
+	struct phy_tdr_config cfg;
+	struct net_device *dev;
+	int ret;
+
+	ret = ethnl_parse_header_dev_get(&req_info,
+					 tb[ETHTOOL_A_CABLE_TEST_TDR_HEADER],
+					 genl_info_net(info), info->extack,
+					 true);
+	if (ret < 0)
+		return ret;
+
+	dev = req_info.dev;
+
+	ret = ethnl_act_cable_test_tdr_cfg(tb[ETHTOOL_A_CABLE_TEST_TDR_CFG],
+					   info, &cfg);
+	if (ret)
+		goto out_dev_put;
+
+	netdev_lock_ops_compat(dev);
+	phydev = ethnl_req_get_phydev(&req_info, tb,
+				      ETHTOOL_A_CABLE_TEST_TDR_HEADER,
+				      info->extack);
+	if (IS_ERR_OR_NULL(phydev)) {
+		ret = -EOPNOTSUPP;
+		goto out_unlock;
+	}
+
+	ops = ethtool_phy_ops;
+	if (!ops || !ops->start_cable_test_tdr) {
+		ret = -EOPNOTSUPP;
+		goto out_unlock;
+	}
+
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		goto out_unlock;
+
+	ret = ops->start_cable_test_tdr(phydev, info->extack, &cfg);
+
+	ethnl_ops_complete(dev);
+
+	if (!ret)
+		ethnl_cable_test_started(phydev,
+					 ETHTOOL_MSG_CABLE_TEST_TDR_NTF);
+
+out_unlock:
+	netdev_unlock_ops_compat(dev);
+out_dev_put:
+	ethnl_parse_header_dev_put(&req_info);
+	return ret;
+}
+
+int ethnl_cable_test_amplitude(struct phy_device *phydev,
+			       u8 pair, s16 mV)
+{
+	struct nlattr *nest;
+	int ret = -EMSGSIZE;
+
+	nest = nla_nest_start(phydev->skb,
+			      ETHTOOL_A_CABLE_TDR_NEST_AMPLITUDE);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_u8(phydev->skb, ETHTOOL_A_CABLE_AMPLITUDE_PAIR, pair))
+		goto err;
+	if (nla_put_u16(phydev->skb, ETHTOOL_A_CABLE_AMPLITUDE_mV, mV))
+		goto err;
+
+	nla_nest_end(phydev->skb, nest);
+	return 0;
+
+err:
+	nla_nest_cancel(phydev->skb, nest);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_amplitude);
+
+int ethnl_cable_test_pulse(struct phy_device *phydev, u16 mV)
+{
+	struct nlattr *nest;
+	int ret = -EMSGSIZE;
+
+	nest = nla_nest_start(phydev->skb, ETHTOOL_A_CABLE_TDR_NEST_PULSE);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_u16(phydev->skb, ETHTOOL_A_CABLE_PULSE_mV, mV))
+		goto err;
+
+	nla_nest_end(phydev->skb, nest);
+	return 0;
+
+err:
+	nla_nest_cancel(phydev->skb, nest);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_pulse);
+
+int ethnl_cable_test_step(struct phy_device *phydev, u32 first, u32 last,
+			  u32 step)
+{
+	struct nlattr *nest;
+	int ret = -EMSGSIZE;
+
+	nest = nla_nest_start(phydev->skb, ETHTOOL_A_CABLE_TDR_NEST_STEP);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_u32(phydev->skb, ETHTOOL_A_CABLE_STEP_FIRST_DISTANCE,
+			first))
+		goto err;
+
+	if (nla_put_u32(phydev->skb, ETHTOOL_A_CABLE_STEP_LAST_DISTANCE, last))
+		goto err;
+
+	if (nla_put_u32(phydev->skb, ETHTOOL_A_CABLE_STEP_STEP_DISTANCE, step))
+		goto err;
+
+	nla_nest_end(phydev->skb, nest);
+	return 0;
+
+err:
+	nla_nest_cancel(phydev->skb, nest);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ethnl_cable_test_step);