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, 226 insertions, 0 deletions

diff --git a/drivers/soc/tegra/flowctrl.c b/drivers/soc/tegra/flowctrl.c
new file mode 100644
index 000000000..221202db3
--- /dev/null
+++ b/drivers/soc/tegra/flowctrl.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * drivers/soc/tegra/flowctrl.c
+ *
+ * Functions and macros to control the flowcontroller
+ *
+ * Copyright (c) 2010-2012, NVIDIA Corporation. All rights reserved.
+ */
+
+#include <linux/cpumask.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+
+#include <soc/tegra/common.h>
+#include <soc/tegra/flowctrl.h>
+#include <soc/tegra/fuse.h>
+
+static u8 flowctrl_offset_halt_cpu[] = {
+	FLOW_CTRL_HALT_CPU0_EVENTS,
+	FLOW_CTRL_HALT_CPU1_EVENTS,
+	FLOW_CTRL_HALT_CPU1_EVENTS + 8,
+	FLOW_CTRL_HALT_CPU1_EVENTS + 16,
+};
+
+static u8 flowctrl_offset_cpu_csr[] = {
+	FLOW_CTRL_CPU0_CSR,
+	FLOW_CTRL_CPU1_CSR,
+	FLOW_CTRL_CPU1_CSR + 8,
+	FLOW_CTRL_CPU1_CSR + 16,
+};
+
+static void __iomem *tegra_flowctrl_base;
+
+static void flowctrl_update(u8 offset, u32 value)
+{
+	if (WARN_ONCE(IS_ERR_OR_NULL(tegra_flowctrl_base),
+		      "Tegra flowctrl not initialised!\n"))
+		return;
+
+	writel(value, tegra_flowctrl_base + offset);
+
+	/* ensure the update has reached the flow controller */
+	wmb();
+	readl_relaxed(tegra_flowctrl_base + offset);
+}
+
+u32 flowctrl_read_cpu_csr(unsigned int cpuid)
+{
+	u8 offset = flowctrl_offset_cpu_csr[cpuid];
+
+	if (WARN_ONCE(IS_ERR_OR_NULL(tegra_flowctrl_base),
+		      "Tegra flowctrl not initialised!\n"))
+		return 0;
+
+	return readl(tegra_flowctrl_base + offset);
+}
+
+void flowctrl_write_cpu_csr(unsigned int cpuid, u32 value)
+{
+	return flowctrl_update(flowctrl_offset_cpu_csr[cpuid], value);
+}
+
+void flowctrl_write_cpu_halt(unsigned int cpuid, u32 value)
+{
+	return flowctrl_update(flowctrl_offset_halt_cpu[cpuid], value);
+}
+
+void flowctrl_cpu_suspend_enter(unsigned int cpuid)
+{
+	unsigned int reg;
+	int i;
+
+	reg = flowctrl_read_cpu_csr(cpuid);
+	switch (tegra_get_chip_id()) {
+	case TEGRA20:
+		/* clear wfe bitmap */
+		reg &= ~TEGRA20_FLOW_CTRL_CSR_WFE_BITMAP;
+		/* clear wfi bitmap */
+		reg &= ~TEGRA20_FLOW_CTRL_CSR_WFI_BITMAP;
+		/* pwr gating on wfe */
+		reg |= TEGRA20_FLOW_CTRL_CSR_WFE_CPU0 << cpuid;
+		break;
+	case TEGRA30:
+	case TEGRA114:
+	case TEGRA124:
+		/* clear wfe bitmap */
+		reg &= ~TEGRA30_FLOW_CTRL_CSR_WFE_BITMAP;
+		/* clear wfi bitmap */
+		reg &= ~TEGRA30_FLOW_CTRL_CSR_WFI_BITMAP;
+
+		if (tegra_get_chip_id() == TEGRA30) {
+			/*
+			 * The wfi doesn't work well on Tegra30 because
+			 * CPU hangs under some odd circumstances after
+			 * power-gating (like memory running off PLLP),
+			 * hence use wfe that is working perfectly fine.
+			 * Note that Tegra30 TRM doc clearly stands that
+			 * wfi should be used for the "Cluster Switching",
+			 * while wfe for the power-gating, just like it
+			 * is done on Tegra20.
+			 */
+			reg |= TEGRA20_FLOW_CTRL_CSR_WFE_CPU0 << cpuid;
+		} else {
+			/* pwr gating on wfi */
+			reg |= TEGRA30_FLOW_CTRL_CSR_WFI_CPU0 << cpuid;
+		}
+		break;
+	}
+	reg |= FLOW_CTRL_CSR_INTR_FLAG;			/* clear intr flag */
+	reg |= FLOW_CTRL_CSR_EVENT_FLAG;		/* clear event flag */
+	reg |= FLOW_CTRL_CSR_ENABLE;			/* pwr gating */
+	flowctrl_write_cpu_csr(cpuid, reg);
+
+	for (i = 0; i < num_possible_cpus(); i++) {
+		if (i == cpuid)
+			continue;
+		reg = flowctrl_read_cpu_csr(i);
+		reg |= FLOW_CTRL_CSR_EVENT_FLAG;
+		reg |= FLOW_CTRL_CSR_INTR_FLAG;
+		flowctrl_write_cpu_csr(i, reg);
+	}
+}
+
+void flowctrl_cpu_suspend_exit(unsigned int cpuid)
+{
+	unsigned int reg;
+
+	/* Disable powergating via flow controller for CPU0 */
+	reg = flowctrl_read_cpu_csr(cpuid);
+	switch (tegra_get_chip_id()) {
+	case TEGRA20:
+		/* clear wfe bitmap */
+		reg &= ~TEGRA20_FLOW_CTRL_CSR_WFE_BITMAP;
+		/* clear wfi bitmap */
+		reg &= ~TEGRA20_FLOW_CTRL_CSR_WFI_BITMAP;
+		break;
+	case TEGRA30:
+	case TEGRA114:
+	case TEGRA124:
+		/* clear wfe bitmap */
+		reg &= ~TEGRA30_FLOW_CTRL_CSR_WFE_BITMAP;
+		/* clear wfi bitmap */
+		reg &= ~TEGRA30_FLOW_CTRL_CSR_WFI_BITMAP;
+		break;
+	}
+	reg &= ~FLOW_CTRL_CSR_ENABLE;			/* clear enable */
+	reg |= FLOW_CTRL_CSR_INTR_FLAG;			/* clear intr */
+	reg |= FLOW_CTRL_CSR_EVENT_FLAG;		/* clear event */
+	flowctrl_write_cpu_csr(cpuid, reg);
+}
+
+static int tegra_flowctrl_probe(struct platform_device *pdev)
+{
+	void __iomem *base = tegra_flowctrl_base;
+
+	tegra_flowctrl_base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(tegra_flowctrl_base))
+		return PTR_ERR(tegra_flowctrl_base);
+
+	iounmap(base);
+
+	return 0;
+}
+
+static const struct of_device_id tegra_flowctrl_match[] = {
+	{ .compatible = "nvidia,tegra210-flowctrl" },
+	{ .compatible = "nvidia,tegra124-flowctrl" },
+	{ .compatible = "nvidia,tegra114-flowctrl" },
+	{ .compatible = "nvidia,tegra30-flowctrl" },
+	{ .compatible = "nvidia,tegra20-flowctrl" },
+	{ }
+};
+
+static struct platform_driver tegra_flowctrl_driver = {
+	.driver = {
+		.name = "tegra-flowctrl",
+		.suppress_bind_attrs = true,
+		.of_match_table = tegra_flowctrl_match,
+	},
+	.probe = tegra_flowctrl_probe,
+};
+builtin_platform_driver(tegra_flowctrl_driver);
+
+static int __init tegra_flowctrl_init(void)
+{
+	struct resource res;
+	struct device_node *np;
+
+	if (!soc_is_tegra())
+		return 0;
+
+	np = of_find_matching_node(NULL, tegra_flowctrl_match);
+	if (np) {
+		if (of_address_to_resource(np, 0, &res) < 0) {
+			pr_err("failed to get flowctrl register\n");
+			return -ENXIO;
+		}
+		of_node_put(np);
+	} else if (IS_ENABLED(CONFIG_ARM)) {
+		/*
+		 * Hardcoded fallback for 32-bit Tegra
+		 * devices if device tree node is missing.
+		 */
+		res.start = 0x60007000;
+		res.end = 0x60007fff;
+		res.flags = IORESOURCE_MEM;
+	} else {
+		/*
+		 * At this point we're running on a Tegra,
+		 * that doesn't support the flow controller
+		 * (eg. Tegra186), so just return.
+		 */
+		return 0;
+	}
+
+	tegra_flowctrl_base = ioremap(res.start, resource_size(&res));
+	if (!tegra_flowctrl_base)
+		return -ENXIO;
+
+	return 0;
+}
+early_initcall(tegra_flowctrl_init);