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, 307 insertions, 0 deletions

diff --git a/drivers/mtd/maps/sa1100-flash.c b/drivers/mtd/maps/sa1100-flash.c
new file mode 100644
index 000000000..4506b27a9
--- /dev/null
+++ b/drivers/mtd/maps/sa1100-flash.c
@@ -0,0 +1,307 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Flash memory access on SA11x0 based devices
+ *
+ * (C) 2000 Nicolas Pitre <nico@fluxnic.net>
+ */
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/platform_device.h>
+#include <linux/err.h>
+#include <linux/io.h>
+
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/map.h>
+#include <linux/mtd/partitions.h>
+#include <linux/mtd/concat.h>
+
+#include <mach/hardware.h>
+#include <linux/sizes.h>
+#include <asm/mach/flash.h>
+
+struct sa_subdev_info {
+	char name[16];
+	struct map_info map;
+	struct mtd_info *mtd;
+	struct flash_platform_data *plat;
+};
+
+struct sa_info {
+	struct mtd_info		*mtd;
+	int			num_subdev;
+	struct sa_subdev_info	subdev[];
+};
+
+static DEFINE_SPINLOCK(sa1100_vpp_lock);
+static int sa1100_vpp_refcnt;
+static void sa1100_set_vpp(struct map_info *map, int on)
+{
+	struct sa_subdev_info *subdev = container_of(map, struct sa_subdev_info, map);
+	unsigned long flags;
+
+	spin_lock_irqsave(&sa1100_vpp_lock, flags);
+	if (on) {
+		if (++sa1100_vpp_refcnt == 1)   /* first nested 'on' */
+			subdev->plat->set_vpp(1);
+	} else {
+		if (--sa1100_vpp_refcnt == 0)   /* last nested 'off' */
+			subdev->plat->set_vpp(0);
+	}
+	spin_unlock_irqrestore(&sa1100_vpp_lock, flags);
+}
+
+static void sa1100_destroy_subdev(struct sa_subdev_info *subdev)
+{
+	if (subdev->mtd)
+		map_destroy(subdev->mtd);
+	if (subdev->map.virt)
+		iounmap(subdev->map.virt);
+	release_mem_region(subdev->map.phys, subdev->map.size);
+}
+
+static int sa1100_probe_subdev(struct sa_subdev_info *subdev, struct resource *res)
+{
+	unsigned long phys;
+	unsigned int size;
+	int ret;
+
+	phys = res->start;
+	size = res->end - phys + 1;
+
+	/*
+	 * Retrieve the bankwidth from the MSC registers.
+	 * We currently only implement CS0 and CS1 here.
+	 */
+	switch (phys) {
+	default:
+		printk(KERN_WARNING "SA1100 flash: unknown base address "
+		       "0x%08lx, assuming CS0\n", phys);
+		fallthrough;
+	case SA1100_CS0_PHYS:
+		subdev->map.bankwidth = (MSC0 & MSC_RBW) ? 2 : 4;
+		break;
+
+	case SA1100_CS1_PHYS:
+		subdev->map.bankwidth = ((MSC0 >> 16) & MSC_RBW) ? 2 : 4;
+		break;
+	}
+
+	if (!request_mem_region(phys, size, subdev->name)) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	if (subdev->plat->set_vpp)
+		subdev->map.set_vpp = sa1100_set_vpp;
+
+	subdev->map.phys = phys;
+	subdev->map.size = size;
+	subdev->map.virt = ioremap(phys, size);
+	if (!subdev->map.virt) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	simple_map_init(&subdev->map);
+
+	/*
+	 * Now let's probe for the actual flash.  Do it here since
+	 * specific machine settings might have been set above.
+	 */
+	subdev->mtd = do_map_probe(subdev->plat->map_name, &subdev->map);
+	if (subdev->mtd == NULL) {
+		ret = -ENXIO;
+		goto err;
+	}
+
+	printk(KERN_INFO "SA1100 flash: CFI device at 0x%08lx, %uMiB, %d-bit\n",
+		phys, (unsigned)(subdev->mtd->size >> 20),
+		subdev->map.bankwidth * 8);
+
+	return 0;
+
+ err:
+	sa1100_destroy_subdev(subdev);
+ out:
+	return ret;
+}
+
+static void sa1100_destroy(struct sa_info *info, struct flash_platform_data *plat)
+{
+	int i;
+
+	if (info->mtd) {
+		mtd_device_unregister(info->mtd);
+		if (info->mtd != info->subdev[0].mtd)
+			mtd_concat_destroy(info->mtd);
+	}
+
+	for (i = info->num_subdev - 1; i >= 0; i--)
+		sa1100_destroy_subdev(&info->subdev[i]);
+	kfree(info);
+
+	if (plat->exit)
+		plat->exit();
+}
+
+static struct sa_info *sa1100_setup_mtd(struct platform_device *pdev,
+					struct flash_platform_data *plat)
+{
+	struct sa_info *info;
+	int nr, i, ret = 0;
+
+	/*
+	 * Count number of devices.
+	 */
+	for (nr = 0; ; nr++)
+		if (!platform_get_resource(pdev, IORESOURCE_MEM, nr))
+			break;
+
+	if (nr == 0) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	/*
+	 * Allocate the map_info structs in one go.
+	 */
+	info = kzalloc_flex(*info, subdev, nr);
+	if (!info) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	if (plat->init) {
+		ret = plat->init();
+		if (ret)
+			goto err;
+	}
+
+	/*
+	 * Claim and then map the memory regions.
+	 */
+	for (i = 0; i < nr; i++) {
+		struct sa_subdev_info *subdev = &info->subdev[i];
+		struct resource *res;
+
+		res = platform_get_resource(pdev, IORESOURCE_MEM, i);
+		if (!res)
+			break;
+
+		subdev->map.name = subdev->name;
+		sprintf(subdev->name, "%s-%d", plat->name, i);
+		subdev->plat = plat;
+
+		ret = sa1100_probe_subdev(subdev, res);
+		if (ret)
+			break;
+	}
+
+	info->num_subdev = i;
+
+	/*
+	 * ENXIO is special.  It means we didn't find a chip when we probed.
+	 */
+	if (ret != 0 && !(ret == -ENXIO && info->num_subdev > 0))
+		goto err;
+
+	/*
+	 * If we found one device, don't bother with concat support.  If
+	 * we found multiple devices, use concat if we have it available,
+	 * otherwise fail.  Either way, it'll be called "sa1100".
+	 */
+	if (info->num_subdev == 1) {
+		strcpy(info->subdev[0].name, plat->name);
+		info->mtd = info->subdev[0].mtd;
+		ret = 0;
+	} else if (info->num_subdev > 1) {
+		struct mtd_info **cdev;
+
+		cdev = kmalloc_objs(*cdev, nr);
+		if (!cdev) {
+			ret = -ENOMEM;
+			goto err;
+		}
+
+		/*
+		 * We detected multiple devices.  Concatenate them together.
+		 */
+		for (i = 0; i < info->num_subdev; i++)
+			cdev[i] = info->subdev[i].mtd;
+
+		info->mtd = mtd_concat_create(cdev, info->num_subdev,
+					      plat->name);
+		kfree(cdev);
+		if (info->mtd == NULL) {
+			ret = -ENXIO;
+			goto err;
+		}
+	}
+	info->mtd->dev.parent = &pdev->dev;
+
+	if (ret == 0)
+		return info;
+
+ err:
+	sa1100_destroy(info, plat);
+ out:
+	return ERR_PTR(ret);
+}
+
+static const char * const part_probes[] = { "cmdlinepart", "RedBoot", NULL };
+
+static int sa1100_mtd_probe(struct platform_device *pdev)
+{
+	struct flash_platform_data *plat = dev_get_platdata(&pdev->dev);
+	struct sa_info *info;
+	int err;
+
+	if (!plat)
+		return -ENODEV;
+
+	info = sa1100_setup_mtd(pdev, plat);
+	if (IS_ERR(info)) {
+		err = PTR_ERR(info);
+		goto out;
+	}
+
+	/*
+	 * Partition selection stuff.
+	 */
+	mtd_device_parse_register(info->mtd, part_probes, NULL, plat->parts,
+				  plat->nr_parts);
+
+	platform_set_drvdata(pdev, info);
+	err = 0;
+
+ out:
+	return err;
+}
+
+static void sa1100_mtd_remove(struct platform_device *pdev)
+{
+	struct sa_info *info = platform_get_drvdata(pdev);
+	struct flash_platform_data *plat = dev_get_platdata(&pdev->dev);
+
+	sa1100_destroy(info, plat);
+}
+
+static struct platform_driver sa1100_mtd_driver = {
+	.probe		= sa1100_mtd_probe,
+	.remove		= sa1100_mtd_remove,
+	.driver		= {
+		.name	= "sa1100-mtd",
+	},
+};
+
+module_platform_driver(sa1100_mtd_driver);
+
+MODULE_AUTHOR("Nicolas Pitre");
+MODULE_DESCRIPTION("SA1100 CFI map driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:sa1100-mtd");