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, 144 insertions, 0 deletions

diff --git a/drivers/soc/versatile/soc-realview.c b/drivers/soc/versatile/soc-realview.c
new file mode 100644
index 000000000..cf91abe07
--- /dev/null
+++ b/drivers/soc/versatile/soc-realview.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2014 Linaro Ltd.
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ */
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/sys_soc.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
+#include <linux/of.h>
+
+/* System ID in syscon */
+#define REALVIEW_SYS_ID_OFFSET 0x00
+
+static const struct of_device_id realview_soc_of_match[] = {
+	{ .compatible = "arm,realview-eb-soc",	},
+	{ .compatible = "arm,realview-pb1176-soc", },
+	{ .compatible = "arm,realview-pb11mp-soc", },
+	{ .compatible = "arm,realview-pba8-soc", },
+	{ .compatible = "arm,realview-pbx-soc", },
+	{ }
+};
+
+static u32 realview_coreid;
+
+static const char *realview_arch_str(u32 id)
+{
+	switch ((id >> 8) & 0xf) {
+	case 0x04:
+		return "AHB";
+	case 0x05:
+		return "Multi-layer AXI";
+	default:
+		return "Unknown";
+	}
+}
+
+static ssize_t
+manufacturer_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%02x\n", realview_coreid >> 24);
+}
+
+static DEVICE_ATTR_RO(manufacturer);
+
+static ssize_t
+board_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "HBI-%03x\n", ((realview_coreid >> 16) & 0xfff));
+}
+
+static DEVICE_ATTR_RO(board);
+
+static ssize_t
+fpga_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s\n", realview_arch_str(realview_coreid));
+}
+
+static DEVICE_ATTR_RO(fpga);
+
+static ssize_t
+build_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%02x\n", (realview_coreid & 0xFF));
+}
+
+static DEVICE_ATTR_RO(build);
+
+static struct attribute *realview_attrs[] = {
+	&dev_attr_manufacturer.attr,
+	&dev_attr_board.attr,
+	&dev_attr_fpga.attr,
+	&dev_attr_build.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(realview);
+
+static void realview_soc_socdev_release(void *data)
+{
+	struct soc_device *soc_dev = data;
+
+	soc_device_unregister(soc_dev);
+}
+
+static int realview_soc_probe(struct platform_device *pdev)
+{
+	struct regmap *syscon_regmap;
+	struct soc_device *soc_dev;
+	struct soc_device_attribute *soc_dev_attr;
+	struct device_node *np = pdev->dev.of_node;
+	int ret;
+
+	syscon_regmap = syscon_regmap_lookup_by_phandle(np, "regmap");
+	if (IS_ERR(syscon_regmap))
+		return PTR_ERR(syscon_regmap);
+
+	soc_dev_attr = devm_kzalloc(&pdev->dev, sizeof(*soc_dev_attr), GFP_KERNEL);
+	if (!soc_dev_attr)
+		return -ENOMEM;
+
+	ret = of_property_read_string(np, "compatible",
+				      &soc_dev_attr->soc_id);
+	if (ret)
+		return -EINVAL;
+
+	soc_dev_attr->machine = "RealView";
+	soc_dev_attr->family = "Versatile";
+	soc_dev_attr->custom_attr_group = realview_groups[0];
+	soc_dev = soc_device_register(soc_dev_attr);
+	if (IS_ERR(soc_dev))
+		return -ENODEV;
+
+	ret = devm_add_action_or_reset(&pdev->dev, realview_soc_socdev_release,
+				       soc_dev);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(syscon_regmap, REALVIEW_SYS_ID_OFFSET,
+			  &realview_coreid);
+	if (ret)
+		return -ENODEV;
+
+	dev_info(&pdev->dev, "RealView Syscon Core ID: 0x%08x, HBI-%03x\n",
+		 realview_coreid,
+		 ((realview_coreid >> 16) & 0xfff));
+	/* FIXME: add attributes for SoC to sysfs */
+	return 0;
+}
+
+static struct platform_driver realview_soc_driver = {
+	.probe = realview_soc_probe,
+	.driver = {
+		.name = "realview-soc",
+		.of_match_table = realview_soc_of_match,
+	},
+};
+builtin_platform_driver(realview_soc_driver);