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, 127 insertions, 0 deletions

diff --git a/drivers/mfd/bcm2835-pm.c b/drivers/mfd/bcm2835-pm.c
new file mode 100644
index 000000000..9e8e3dcf4
--- /dev/null
+++ b/drivers/mfd/bcm2835-pm.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * PM MFD driver for Broadcom BCM2835
+ *
+ * This driver binds to the PM block and creates the MFD device for
+ * the WDT and power drivers.
+ */
+
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/mfd/bcm2835-pm.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <linux/watchdog.h>
+
+static const struct mfd_cell bcm2835_pm_devs[] = {
+	{ .name = "bcm2835-wdt" },
+};
+
+static const struct mfd_cell bcm2835_power_devs[] = {
+	{ .name = "bcm2835-power" },
+};
+
+static int bcm2835_pm_get_pdata(struct platform_device *pdev,
+				struct bcm2835_pm *pm)
+{
+	if (of_property_present(pm->dev->of_node, "reg-names")) {
+		struct resource *res;
+
+		pm->base = devm_platform_ioremap_resource_byname(pdev, "pm");
+		if (IS_ERR(pm->base))
+			return PTR_ERR(pm->base);
+
+		res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "asb");
+		if (res) {
+			pm->asb = devm_ioremap_resource(&pdev->dev, res);
+			if (IS_ERR(pm->asb))
+				pm->asb = NULL;
+		}
+
+		res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
+						    "rpivid_asb");
+		if (res) {
+			pm->rpivid_asb = devm_ioremap_resource(&pdev->dev, res);
+			if (IS_ERR(pm->rpivid_asb))
+				pm->rpivid_asb = NULL;
+		}
+
+		return 0;
+	}
+
+	/* If no 'reg-names' property is found we can assume we're using old DTB. */
+	pm->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(pm->base))
+		return PTR_ERR(pm->base);
+
+	pm->asb = devm_platform_ioremap_resource(pdev, 1);
+	if (IS_ERR(pm->asb))
+		pm->asb = NULL;
+
+	pm->rpivid_asb = devm_platform_ioremap_resource(pdev, 2);
+	if (IS_ERR(pm->rpivid_asb))
+		pm->rpivid_asb = NULL;
+
+	return 0;
+}
+
+static int bcm2835_pm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct bcm2835_pm *pm;
+	int ret;
+
+	pm = devm_kzalloc(dev, sizeof(*pm), GFP_KERNEL);
+	if (!pm)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, pm);
+
+	pm->dev = dev;
+	pm->soc = (uintptr_t)device_get_match_data(dev);
+
+	ret = bcm2835_pm_get_pdata(pdev, pm);
+	if (ret)
+		return ret;
+
+	ret = devm_mfd_add_devices(dev, -1,
+				   bcm2835_pm_devs, ARRAY_SIZE(bcm2835_pm_devs),
+				   NULL, 0, NULL);
+	if (ret)
+		return ret;
+
+	/*
+	 * We'll use the presence of the AXI ASB regs in the
+	 * bcm2835-pm binding as the key for whether we can reference
+	 * the full PM register range and support power domains.
+	 */
+	if (pm->asb || pm->soc == BCM2835_PM_SOC_BCM2712)
+		return devm_mfd_add_devices(dev, -1, bcm2835_power_devs,
+					    ARRAY_SIZE(bcm2835_power_devs),
+					    NULL, 0, NULL);
+	return 0;
+}
+
+static const struct of_device_id bcm2835_pm_of_match[] = {
+	{ .compatible = "brcm,bcm2835-pm-wdt", },
+	{ .compatible = "brcm,bcm2835-pm", .data = (void *)BCM2835_PM_SOC_BCM2835 },
+	{ .compatible = "brcm,bcm2711-pm", .data = (void *)BCM2835_PM_SOC_BCM2711 },
+	{ .compatible = "brcm,bcm2712-pm", .data = (void *)BCM2835_PM_SOC_BCM2712 },
+	{},
+};
+MODULE_DEVICE_TABLE(of, bcm2835_pm_of_match);
+
+static struct platform_driver bcm2835_pm_driver = {
+	.probe		= bcm2835_pm_probe,
+	.driver = {
+		.name =	"bcm2835-pm",
+		.of_match_table = bcm2835_pm_of_match,
+	},
+};
+module_platform_driver(bcm2835_pm_driver);
+
+MODULE_AUTHOR("Eric Anholt <eric@anholt.net>");
+MODULE_DESCRIPTION("Driver for Broadcom BCM2835 PM MFD");