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, 265 insertions, 0 deletions

diff --git a/drivers/net/netdevsim/psample.c b/drivers/net/netdevsim/psample.c
new file mode 100644
index 000000000..1e71c3da4
--- /dev/null
+++ b/drivers/net/netdevsim/psample.c
@@ -0,0 +1,265 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Mellanox Technologies. All rights reserved */
+
+#include <linux/debugfs.h>
+#include <linux/err.h>
+#include <linux/etherdevice.h>
+#include <linux/inet.h>
+#include <linux/kernel.h>
+#include <linux/random.h>
+#include <linux/slab.h>
+#include <net/devlink.h>
+#include <net/ip.h>
+#include <net/psample.h>
+#include <uapi/linux/ip.h>
+#include <uapi/linux/udp.h>
+
+#include "netdevsim.h"
+
+#define NSIM_PSAMPLE_REPORT_INTERVAL_MS	100
+#define NSIM_PSAMPLE_INVALID_TC		0xFFFF
+#define NSIM_PSAMPLE_L4_DATA_LEN	100
+
+struct nsim_dev_psample {
+	struct delayed_work psample_dw;
+	struct dentry *ddir;
+	struct psample_group *group;
+	u32 rate;
+	u32 group_num;
+	u32 trunc_size;
+	int in_ifindex;
+	int out_ifindex;
+	u16 out_tc;
+	u64 out_tc_occ_max;
+	u64 latency_max;
+	bool is_active;
+};
+
+static struct sk_buff *nsim_dev_psample_skb_build(void)
+{
+	int tot_len, data_len = NSIM_PSAMPLE_L4_DATA_LEN;
+	struct sk_buff *skb;
+	struct udphdr *udph;
+	struct ethhdr *eth;
+	struct iphdr *iph;
+
+	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
+	if (!skb)
+		return NULL;
+	tot_len = sizeof(struct iphdr) + sizeof(struct udphdr) + data_len;
+
+	skb_reset_mac_header(skb);
+	eth = skb_put(skb, sizeof(struct ethhdr));
+	eth_random_addr(eth->h_dest);
+	eth_random_addr(eth->h_source);
+	eth->h_proto = htons(ETH_P_IP);
+	skb->protocol = htons(ETH_P_IP);
+
+	skb_set_network_header(skb, skb->len);
+	iph = skb_put(skb, sizeof(struct iphdr));
+	iph->protocol = IPPROTO_UDP;
+	iph->saddr = in_aton("192.0.2.1");
+	iph->daddr = in_aton("198.51.100.1");
+	iph->version = 0x4;
+	iph->frag_off = 0;
+	iph->ihl = 0x5;
+	iph->tot_len = htons(tot_len);
+	iph->id = 0;
+	iph->ttl = 100;
+	iph->check = 0;
+	iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
+
+	skb_set_transport_header(skb, skb->len);
+	udph = skb_put_zero(skb, sizeof(struct udphdr) + data_len);
+	get_random_bytes(&udph->source, sizeof(u16));
+	get_random_bytes(&udph->dest, sizeof(u16));
+	udp_set_len_short(udph, sizeof(struct udphdr) + data_len);
+
+	return skb;
+}
+
+static void nsim_dev_psample_md_prepare(const struct nsim_dev_psample *psample,
+					struct psample_metadata *md,
+					unsigned int len)
+{
+	md->trunc_size = psample->trunc_size ? psample->trunc_size : len;
+	md->in_ifindex = psample->in_ifindex;
+	md->out_ifindex = psample->out_ifindex;
+
+	if (psample->out_tc != NSIM_PSAMPLE_INVALID_TC) {
+		md->out_tc = psample->out_tc;
+		md->out_tc_valid = 1;
+	}
+
+	if (psample->out_tc_occ_max) {
+		u64 out_tc_occ;
+
+		out_tc_occ = get_random_u64();
+		md->out_tc_occ = out_tc_occ & (psample->out_tc_occ_max - 1);
+		md->out_tc_occ_valid = 1;
+	}
+
+	if (psample->latency_max) {
+		u64 latency;
+
+		latency = get_random_u64();
+		md->latency = latency & (psample->latency_max - 1);
+		md->latency_valid = 1;
+	}
+}
+
+static void nsim_dev_psample_report_work(struct work_struct *work)
+{
+	struct nsim_dev_psample *psample;
+	struct psample_metadata md = {};
+	struct sk_buff *skb;
+	unsigned long delay;
+
+	psample = container_of(work, struct nsim_dev_psample, psample_dw.work);
+
+	skb = nsim_dev_psample_skb_build();
+	if (!skb)
+		goto out;
+
+	nsim_dev_psample_md_prepare(psample, &md, skb->len);
+	psample_sample_packet(psample->group, skb, psample->rate, &md);
+	consume_skb(skb);
+
+out:
+	delay = msecs_to_jiffies(NSIM_PSAMPLE_REPORT_INTERVAL_MS);
+	schedule_delayed_work(&psample->psample_dw, delay);
+}
+
+static int nsim_dev_psample_enable(struct nsim_dev *nsim_dev)
+{
+	struct nsim_dev_psample *psample = nsim_dev->psample;
+	struct devlink *devlink;
+	unsigned long delay;
+
+	if (psample->is_active)
+		return -EBUSY;
+
+	devlink = priv_to_devlink(nsim_dev);
+	psample->group = psample_group_get(devlink_net(devlink),
+					   psample->group_num);
+	if (!psample->group)
+		return -EINVAL;
+
+	delay = msecs_to_jiffies(NSIM_PSAMPLE_REPORT_INTERVAL_MS);
+	schedule_delayed_work(&psample->psample_dw, delay);
+
+	psample->is_active = true;
+
+	return 0;
+}
+
+static int nsim_dev_psample_disable(struct nsim_dev *nsim_dev)
+{
+	struct nsim_dev_psample *psample = nsim_dev->psample;
+
+	if (!psample->is_active)
+		return -EINVAL;
+
+	psample->is_active = false;
+
+	cancel_delayed_work_sync(&psample->psample_dw);
+	psample_group_put(psample->group);
+
+	return 0;
+}
+
+static ssize_t nsim_dev_psample_enable_write(struct file *file,
+					     const char __user *data,
+					     size_t count, loff_t *ppos)
+{
+	struct nsim_dev *nsim_dev = file->private_data;
+	bool enable;
+	int err;
+
+	err = kstrtobool_from_user(data, count, &enable);
+	if (err)
+		return err;
+
+	if (enable)
+		err = nsim_dev_psample_enable(nsim_dev);
+	else
+		err = nsim_dev_psample_disable(nsim_dev);
+
+	return err ? err : count;
+}
+
+static const struct file_operations nsim_psample_enable_fops = {
+	.open = simple_open,
+	.write = nsim_dev_psample_enable_write,
+	.llseek = generic_file_llseek,
+	.owner = THIS_MODULE,
+};
+
+int nsim_dev_psample_init(struct nsim_dev *nsim_dev)
+{
+	struct nsim_dev_psample *psample;
+	int err;
+
+	psample = kzalloc_obj(*psample);
+	if (!psample)
+		return -ENOMEM;
+	nsim_dev->psample = psample;
+
+	INIT_DELAYED_WORK(&psample->psample_dw, nsim_dev_psample_report_work);
+
+	psample->ddir = debugfs_create_dir("psample", nsim_dev->ddir);
+	if (IS_ERR(psample->ddir)) {
+		err = PTR_ERR(psample->ddir);
+		goto err_psample_free;
+	}
+
+	/* Populate sampling parameters with sane defaults. */
+	psample->rate = 100;
+	debugfs_create_u32("rate", 0600, psample->ddir, &psample->rate);
+
+	psample->group_num = 10;
+	debugfs_create_u32("group_num", 0600, psample->ddir,
+			   &psample->group_num);
+
+	psample->trunc_size = 0;
+	debugfs_create_u32("trunc_size", 0600, psample->ddir,
+			   &psample->trunc_size);
+
+	psample->in_ifindex = 1;
+	debugfs_create_u32("in_ifindex", 0600, psample->ddir,
+			   &psample->in_ifindex);
+
+	psample->out_ifindex = 2;
+	debugfs_create_u32("out_ifindex", 0600, psample->ddir,
+			   &psample->out_ifindex);
+
+	psample->out_tc = 0;
+	debugfs_create_u16("out_tc", 0600, psample->ddir, &psample->out_tc);
+
+	psample->out_tc_occ_max = 10000;
+	debugfs_create_u64("out_tc_occ_max", 0600, psample->ddir,
+			   &psample->out_tc_occ_max);
+
+	psample->latency_max = 50;
+	debugfs_create_u64("latency_max", 0600, psample->ddir,
+			   &psample->latency_max);
+
+	debugfs_create_file("enable", 0200, psample->ddir, nsim_dev,
+			    &nsim_psample_enable_fops);
+
+	return 0;
+
+err_psample_free:
+	kfree(nsim_dev->psample);
+	return err;
+}
+
+void nsim_dev_psample_exit(struct nsim_dev *nsim_dev)
+{
+	debugfs_remove_recursive(nsim_dev->psample->ddir);
+	if (nsim_dev->psample->is_active) {
+		cancel_delayed_work_sync(&nsim_dev->psample->psample_dw);
+		psample_group_put(nsim_dev->psample->group);
+	}
+	kfree(nsim_dev->psample);
+}