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, 276 insertions, 0 deletions

diff --git a/drivers/bcma/host_soc.c b/drivers/bcma/host_soc.c
new file mode 100644
index 000000000..20b1816c5
--- /dev/null
+++ b/drivers/bcma/host_soc.c
@@ -0,0 +1,276 @@
+/*
+ * Broadcom specific AMBA
+ * System on Chip (SoC) Host
+ *
+ * Licensed under the GNU/GPL. See COPYING for details.
+ */
+
+#include "bcma_private.h"
+#include "scan.h"
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/bcma/bcma.h>
+#include <linux/bcma/bcma_soc.h>
+
+static u8 bcma_host_soc_read8(struct bcma_device *core, u16 offset)
+{
+	return readb(core->io_addr + offset);
+}
+
+static u16 bcma_host_soc_read16(struct bcma_device *core, u16 offset)
+{
+	return readw(core->io_addr + offset);
+}
+
+static u32 bcma_host_soc_read32(struct bcma_device *core, u16 offset)
+{
+	return readl(core->io_addr + offset);
+}
+
+static void bcma_host_soc_write8(struct bcma_device *core, u16 offset,
+				 u8 value)
+{
+	writeb(value, core->io_addr + offset);
+}
+
+static void bcma_host_soc_write16(struct bcma_device *core, u16 offset,
+				 u16 value)
+{
+	writew(value, core->io_addr + offset);
+}
+
+static void bcma_host_soc_write32(struct bcma_device *core, u16 offset,
+				 u32 value)
+{
+	writel(value, core->io_addr + offset);
+}
+
+#ifdef CONFIG_BCMA_BLOCKIO
+static void bcma_host_soc_block_read(struct bcma_device *core, void *buffer,
+				     size_t count, u16 offset, u8 reg_width)
+{
+	void __iomem *addr = core->io_addr + offset;
+
+	switch (reg_width) {
+	case sizeof(u8): {
+		u8 *buf = buffer;
+
+		while (count) {
+			*buf = __raw_readb(addr);
+			buf++;
+			count--;
+		}
+		break;
+	}
+	case sizeof(u16): {
+		__le16 *buf = buffer;
+
+		WARN_ON(count & 1);
+		while (count) {
+			*buf = (__force __le16)__raw_readw(addr);
+			buf++;
+			count -= 2;
+		}
+		break;
+	}
+	case sizeof(u32): {
+		__le32 *buf = buffer;
+
+		WARN_ON(count & 3);
+		while (count) {
+			*buf = (__force __le32)__raw_readl(addr);
+			buf++;
+			count -= 4;
+		}
+		break;
+	}
+	default:
+		WARN_ON(1);
+	}
+}
+
+static void bcma_host_soc_block_write(struct bcma_device *core,
+				      const void *buffer,
+				      size_t count, u16 offset, u8 reg_width)
+{
+	void __iomem *addr = core->io_addr + offset;
+
+	switch (reg_width) {
+	case sizeof(u8): {
+		const u8 *buf = buffer;
+
+		while (count) {
+			__raw_writeb(*buf, addr);
+			buf++;
+			count--;
+		}
+		break;
+	}
+	case sizeof(u16): {
+		const __le16 *buf = buffer;
+
+		WARN_ON(count & 1);
+		while (count) {
+			__raw_writew((__force u16)(*buf), addr);
+			buf++;
+			count -= 2;
+		}
+		break;
+	}
+	case sizeof(u32): {
+		const __le32 *buf = buffer;
+
+		WARN_ON(count & 3);
+		while (count) {
+			__raw_writel((__force u32)(*buf), addr);
+			buf++;
+			count -= 4;
+		}
+		break;
+	}
+	default:
+		WARN_ON(1);
+	}
+}
+#endif /* CONFIG_BCMA_BLOCKIO */
+
+static u32 bcma_host_soc_aread32(struct bcma_device *core, u16 offset)
+{
+	if (WARN_ONCE(!core->io_wrap, "Accessed core has no wrapper/agent\n"))
+		return ~0;
+	return readl(core->io_wrap + offset);
+}
+
+static void bcma_host_soc_awrite32(struct bcma_device *core, u16 offset,
+				  u32 value)
+{
+	if (WARN_ONCE(!core->io_wrap, "Accessed core has no wrapper/agent\n"))
+		return;
+	writel(value, core->io_wrap + offset);
+}
+
+static const struct bcma_host_ops bcma_host_soc_ops = {
+	.read8		= bcma_host_soc_read8,
+	.read16		= bcma_host_soc_read16,
+	.read32		= bcma_host_soc_read32,
+	.write8		= bcma_host_soc_write8,
+	.write16	= bcma_host_soc_write16,
+	.write32	= bcma_host_soc_write32,
+#ifdef CONFIG_BCMA_BLOCKIO
+	.block_read	= bcma_host_soc_block_read,
+	.block_write	= bcma_host_soc_block_write,
+#endif
+	.aread32	= bcma_host_soc_aread32,
+	.awrite32	= bcma_host_soc_awrite32,
+};
+
+int __init bcma_host_soc_register(struct bcma_soc *soc)
+{
+	struct bcma_bus *bus = &soc->bus;
+
+	/* iomap only first core. We have to read some register on this core
+	 * to scan the bus.
+	 */
+	bus->mmio = ioremap(BCMA_ADDR_BASE, BCMA_CORE_SIZE * 1);
+	if (!bus->mmio)
+		return -ENOMEM;
+
+	/* Host specific */
+	bus->hosttype = BCMA_HOSTTYPE_SOC;
+	bus->ops = &bcma_host_soc_ops;
+
+	/* Initialize struct, detect chip */
+	bcma_init_bus(bus);
+
+	return 0;
+}
+
+int __init bcma_host_soc_init(struct bcma_soc *soc)
+{
+	struct bcma_bus *bus = &soc->bus;
+	int err;
+
+	/* Scan bus and initialize it */
+	err = bcma_bus_early_register(bus);
+	if (err)
+		iounmap(bus->mmio);
+
+	return err;
+}
+
+#ifdef CONFIG_OF
+static int bcma_host_soc_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct bcma_bus *bus;
+	int err;
+
+	/* Alloc */
+	bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
+	if (!bus)
+		return -ENOMEM;
+
+	bus->dev = dev;
+
+	/* Map MMIO */
+	bus->mmio = of_iomap(np, 0);
+	if (!bus->mmio)
+		return -ENOMEM;
+
+	/* Host specific */
+	bus->hosttype = BCMA_HOSTTYPE_SOC;
+	bus->ops = &bcma_host_soc_ops;
+
+	/* Initialize struct, detect chip */
+	bcma_init_bus(bus);
+
+	/* Register */
+	err = bcma_bus_register(bus);
+	if (err)
+		goto err_unmap_mmio;
+
+	platform_set_drvdata(pdev, bus);
+
+	return err;
+
+err_unmap_mmio:
+	iounmap(bus->mmio);
+	return err;
+}
+
+static void bcma_host_soc_remove(struct platform_device *pdev)
+{
+	struct bcma_bus *bus = platform_get_drvdata(pdev);
+
+	bcma_bus_unregister(bus);
+	iounmap(bus->mmio);
+	platform_set_drvdata(pdev, NULL);
+}
+
+static const struct of_device_id bcma_host_soc_of_match[] = {
+	{ .compatible = "brcm,bus-axi", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, bcma_host_soc_of_match);
+
+static struct platform_driver bcma_host_soc_driver = {
+	.driver = {
+		.name = "bcma-host-soc",
+		.of_match_table = bcma_host_soc_of_match,
+	},
+	.probe		= bcma_host_soc_probe,
+	.remove		= bcma_host_soc_remove,
+};
+
+int __init bcma_host_soc_register_driver(void)
+{
+	return platform_driver_register(&bcma_host_soc_driver);
+}
+
+void __exit bcma_host_soc_unregister_driver(void)
+{
+	platform_driver_unregister(&bcma_host_soc_driver);
+}
+#endif /* CONFIG_OF */