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, 129 insertions, 0 deletions

diff --git a/drivers/zorro/proc.c b/drivers/zorro/proc.c
new file mode 100644
index 000000000..f916bf60b
--- /dev/null
+++ b/drivers/zorro/proc.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *	Procfs interface for the Zorro bus.
+ *
+ *	Copyright (C) 1998-2003 Geert Uytterhoeven
+ *
+ *	Heavily based on the procfs interface for the PCI bus, which is
+ *
+ *	Copyright (C) 1997, 1998 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
+ */
+
+#include <linux/types.h>
+#include <linux/zorro.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/init.h>
+#include <linux/export.h>
+
+#include <asm/byteorder.h>
+#include <linux/uaccess.h>
+#include <asm/amigahw.h>
+#include <asm/setup.h>
+
+static loff_t
+proc_bus_zorro_lseek(struct file *file, loff_t off, int whence)
+{
+	return fixed_size_llseek(file, off, whence, sizeof(struct ConfigDev));
+}
+
+static ssize_t
+proc_bus_zorro_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+	struct zorro_dev *z = pde_data(file_inode(file));
+	struct ConfigDev cd;
+	loff_t pos = *ppos;
+
+	if (pos >= sizeof(struct ConfigDev))
+		return 0;
+	if (nbytes >= sizeof(struct ConfigDev))
+		nbytes = sizeof(struct ConfigDev);
+	if (pos + nbytes > sizeof(struct ConfigDev))
+		nbytes = sizeof(struct ConfigDev) - pos;
+
+	/* Construct a ConfigDev */
+	memset(&cd, 0, sizeof(cd));
+	cd.cd_Rom = z->rom;
+	cd.cd_SlotAddr = cpu_to_be16(z->slotaddr);
+	cd.cd_SlotSize = cpu_to_be16(z->slotsize);
+	cd.cd_BoardAddr = cpu_to_be32(zorro_resource_start(z));
+	cd.cd_BoardSize = cpu_to_be32(zorro_resource_len(z));
+
+	if (copy_to_user(buf, (void *)&cd + pos, nbytes))
+		return -EFAULT;
+	*ppos += nbytes;
+
+	return nbytes;
+}
+
+static const struct proc_ops bus_zorro_proc_ops = {
+	.proc_lseek	= proc_bus_zorro_lseek,
+	.proc_read	= proc_bus_zorro_read,
+};
+
+static void * zorro_seq_start(struct seq_file *m, loff_t *pos)
+{
+	return (*pos < zorro_num_autocon) ? pos : NULL;
+}
+
+static void * zorro_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	(*pos)++;
+	return (*pos < zorro_num_autocon) ? pos : NULL;
+}
+
+static void zorro_seq_stop(struct seq_file *m, void *v)
+{
+}
+
+static int zorro_seq_show(struct seq_file *m, void *v)
+{
+	unsigned int slot = *(loff_t *)v;
+	struct zorro_dev *z = &zorro_autocon[slot];
+
+	seq_printf(m, "%02x\t%08x\t%08lx\t%08lx\t%02x\n", slot, z->id,
+		   (unsigned long)zorro_resource_start(z),
+		   (unsigned long)zorro_resource_len(z),
+		   z->rom.er_Type);
+	return 0;
+}
+
+static const struct seq_operations zorro_devices_seq_ops = {
+	.start = zorro_seq_start,
+	.next  = zorro_seq_next,
+	.stop  = zorro_seq_stop,
+	.show  = zorro_seq_show,
+};
+
+static struct proc_dir_entry *proc_bus_zorro_dir;
+
+static int __init zorro_proc_attach_device(unsigned int slot)
+{
+	struct proc_dir_entry *entry;
+	char name[4];
+
+	sprintf(name, "%02x", slot);
+	entry = proc_create_data(name, 0, proc_bus_zorro_dir,
+				 &bus_zorro_proc_ops,
+				 &zorro_autocon[slot]);
+	if (!entry)
+		return -ENOMEM;
+	proc_set_size(entry, sizeof(struct zorro_dev));
+	return 0;
+}
+
+static int __init zorro_proc_init(void)
+{
+	unsigned int slot;
+
+	if (MACH_IS_AMIGA && AMIGAHW_PRESENT(ZORRO)) {
+		proc_bus_zorro_dir = proc_mkdir("bus/zorro", NULL);
+		proc_create_seq("devices", 0, proc_bus_zorro_dir,
+			    &zorro_devices_seq_ops);
+		for (slot = 0; slot < zorro_num_autocon; slot++)
+			zorro_proc_attach_device(slot);
+	}
+	return 0;
+}
+
+device_initcall(zorro_proc_init);