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, 341 insertions, 0 deletions

diff --git a/drivers/char/agp/backend.c b/drivers/char/agp/backend.c
new file mode 100644
index 000000000..8983addca
--- /dev/null
+++ b/drivers/char/agp/backend.c
@@ -0,0 +1,341 @@
+/*
+ * AGPGART driver backend routines.
+ * Copyright (C) 2004 Silicon Graphics, Inc.
+ * Copyright (C) 2002-2003 Dave Jones.
+ * Copyright (C) 1999 Jeff Hartmann.
+ * Copyright (C) 1999 Precision Insight, Inc.
+ * Copyright (C) 1999 Xi Graphics, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * JEFF HARTMANN, DAVE JONES, OR ANY OTHER CONTRIBUTORS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
+ * OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * TODO:
+ * - Allocate more than order 0 pages to avoid too much linear map splitting.
+ */
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/pagemap.h>
+#include <linux/miscdevice.h>
+#include <linux/pm.h>
+#include <linux/agp_backend.h>
+#include <linux/agpgart.h>
+#include <linux/vmalloc.h>
+#include <asm/io.h>
+#include "agp.h"
+
+/* Due to XFree86 brain-damage, we can't go to 1.0 until they
+ * fix some real stupidity. It's only by chance we can bump
+ * past 0.99 at all due to some boolean logic error. */
+#define AGPGART_VERSION_MAJOR 0
+#define AGPGART_VERSION_MINOR 103
+static const struct agp_version agp_current_version =
+{
+	.major = AGPGART_VERSION_MAJOR,
+	.minor = AGPGART_VERSION_MINOR,
+};
+
+struct agp_bridge_data *(*agp_find_bridge)(struct pci_dev *) =
+	&agp_generic_find_bridge;
+
+struct agp_bridge_data *agp_bridge;
+LIST_HEAD(agp_bridges);
+EXPORT_SYMBOL(agp_bridge);
+EXPORT_SYMBOL(agp_bridges);
+EXPORT_SYMBOL(agp_find_bridge);
+
+/**
+ *	agp_backend_acquire  -  attempt to acquire an agp backend.
+ *	@pdev: the PCI device
+ *
+ */
+struct agp_bridge_data *agp_backend_acquire(struct pci_dev *pdev)
+{
+	struct agp_bridge_data *bridge;
+
+	bridge = agp_find_bridge(pdev);
+
+	if (!bridge)
+		return NULL;
+
+	if (atomic_read(&bridge->agp_in_use))
+		return NULL;
+	atomic_inc(&bridge->agp_in_use);
+	return bridge;
+}
+EXPORT_SYMBOL(agp_backend_acquire);
+
+
+/**
+ *	agp_backend_release  -  release the lock on the agp backend.
+ *	@bridge: the AGP backend to release
+ *
+ *	The caller must insure that the graphics aperture translation table
+ *	is read for use by another entity.
+ *
+ *	(Ensure that all memory it bound is unbound.)
+ */
+void agp_backend_release(struct agp_bridge_data *bridge)
+{
+
+	if (bridge)
+		atomic_dec(&bridge->agp_in_use);
+}
+EXPORT_SYMBOL(agp_backend_release);
+
+
+static const struct { int mem, agp; } maxes_table[] = {
+	{0, 0},
+	{32, 4},
+	{64, 28},
+	{128, 96},
+	{256, 204},
+	{512, 440},
+	{1024, 942},
+	{2048, 1920},
+	{4096, 3932}
+};
+
+static int agp_find_max(void)
+{
+	long memory, index, result;
+
+#if PAGE_SHIFT < 20
+	memory = totalram_pages() >> (20 - PAGE_SHIFT);
+#else
+	memory = totalram_pages() << (PAGE_SHIFT - 20);
+#endif
+	index = 1;
+
+	while ((memory > maxes_table[index].mem) && (index < 8))
+		index++;
+
+	result = maxes_table[index - 1].agp +
+	   ( (memory - maxes_table[index - 1].mem)  *
+	     (maxes_table[index].agp - maxes_table[index - 1].agp)) /
+	   (maxes_table[index].mem - maxes_table[index - 1].mem);
+
+	result = result << (20 - PAGE_SHIFT);
+	return result;
+}
+
+
+static int agp_backend_initialize(struct agp_bridge_data *bridge)
+{
+	int size_value, rc, got_gatt=0, got_keylist=0;
+
+	bridge->max_memory_agp = agp_find_max();
+	bridge->version = &agp_current_version;
+
+	if (bridge->driver->needs_scratch_page) {
+		struct page *page = bridge->driver->agp_alloc_page(bridge);
+
+		if (!page) {
+			dev_err(&bridge->dev->dev,
+				"can't get memory for scratch page\n");
+			return -ENOMEM;
+		}
+
+		bridge->scratch_page_page = page;
+		bridge->scratch_page_dma = page_to_phys(page);
+
+		bridge->scratch_page = bridge->driver->mask_memory(bridge,
+						   bridge->scratch_page_dma, 0);
+	}
+
+	size_value = bridge->driver->fetch_size();
+	if (size_value == 0) {
+		dev_err(&bridge->dev->dev, "can't determine aperture size\n");
+		rc = -EINVAL;
+		goto err_out;
+	}
+	if (bridge->driver->create_gatt_table(bridge)) {
+		dev_err(&bridge->dev->dev,
+			"can't get memory for graphics translation table\n");
+		rc = -ENOMEM;
+		goto err_out;
+	}
+	got_gatt = 1;
+
+	bridge->key_list = vzalloc(PAGE_SIZE * 4);
+	if (bridge->key_list == NULL) {
+		dev_err(&bridge->dev->dev,
+			"can't allocate memory for key lists\n");
+		rc = -ENOMEM;
+		goto err_out;
+	}
+	got_keylist = 1;
+
+	/* FIXME vmalloc'd memory not guaranteed contiguous */
+
+	if (bridge->driver->configure()) {
+		dev_err(&bridge->dev->dev, "error configuring host chipset\n");
+		rc = -EINVAL;
+		goto err_out;
+	}
+	INIT_LIST_HEAD(&bridge->mapped_list);
+	spin_lock_init(&bridge->mapped_lock);
+
+	return 0;
+
+err_out:
+	if (bridge->driver->needs_scratch_page) {
+		struct page *page = bridge->scratch_page_page;
+
+		bridge->driver->agp_destroy_page(page, AGP_PAGE_DESTROY_UNMAP);
+		bridge->driver->agp_destroy_page(page, AGP_PAGE_DESTROY_FREE);
+	}
+	if (got_gatt)
+		bridge->driver->free_gatt_table(bridge);
+	if (got_keylist) {
+		vfree(bridge->key_list);
+		bridge->key_list = NULL;
+	}
+	return rc;
+}
+
+/* cannot be __exit b/c as it could be called from __init code */
+static void agp_backend_cleanup(struct agp_bridge_data *bridge)
+{
+	if (bridge->driver->cleanup)
+		bridge->driver->cleanup();
+	if (bridge->driver->free_gatt_table)
+		bridge->driver->free_gatt_table(bridge);
+
+	vfree(bridge->key_list);
+	bridge->key_list = NULL;
+
+	if (bridge->driver->agp_destroy_page &&
+	    bridge->driver->needs_scratch_page) {
+		struct page *page = bridge->scratch_page_page;
+
+		bridge->driver->agp_destroy_page(page, AGP_PAGE_DESTROY_UNMAP);
+		bridge->driver->agp_destroy_page(page, AGP_PAGE_DESTROY_FREE);
+	}
+}
+
+/* When we remove the global variable agp_bridge from all drivers
+ * then agp_alloc_bridge and agp_generic_find_bridge need to be updated
+ */
+
+struct agp_bridge_data *agp_alloc_bridge(void)
+{
+	struct agp_bridge_data *bridge;
+
+	bridge = kzalloc_obj(*bridge);
+	if (!bridge)
+		return NULL;
+
+	atomic_set(&bridge->agp_in_use, 0);
+	atomic_set(&bridge->current_memory_agp, 0);
+
+	if (list_empty(&agp_bridges))
+		agp_bridge = bridge;
+
+	return bridge;
+}
+EXPORT_SYMBOL(agp_alloc_bridge);
+
+
+void agp_put_bridge(struct agp_bridge_data *bridge)
+{
+        kfree(bridge);
+
+        if (list_empty(&agp_bridges))
+                agp_bridge = NULL;
+}
+EXPORT_SYMBOL(agp_put_bridge);
+
+
+int agp_add_bridge(struct agp_bridge_data *bridge)
+{
+	int error;
+
+	if (agp_off) {
+		error = -ENODEV;
+		goto err_put_bridge;
+	}
+
+	if (!bridge->dev) {
+		printk (KERN_DEBUG PFX "Erk, registering with no pci_dev!\n");
+		error = -EINVAL;
+		goto err_put_bridge;
+	}
+
+	/* Grab reference on the chipset driver. */
+	if (!try_module_get(bridge->driver->owner)) {
+		dev_info(&bridge->dev->dev, "can't lock chipset driver\n");
+		error = -EINVAL;
+		goto err_put_bridge;
+	}
+
+	error = agp_backend_initialize(bridge);
+	if (error) {
+		dev_info(&bridge->dev->dev,
+			 "agp_backend_initialize() failed\n");
+		goto err_out;
+	}
+
+	if (list_empty(&agp_bridges)) {
+		dev_info(&bridge->dev->dev, "AGP aperture is %dM @ 0x%lx\n",
+			 bridge->driver->fetch_size(), bridge->gart_bus_addr);
+
+	}
+
+	list_add(&bridge->list, &agp_bridges);
+	return 0;
+
+err_out:
+	module_put(bridge->driver->owner);
+err_put_bridge:
+	agp_put_bridge(bridge);
+	return error;
+}
+EXPORT_SYMBOL_GPL(agp_add_bridge);
+
+
+void agp_remove_bridge(struct agp_bridge_data *bridge)
+{
+	agp_backend_cleanup(bridge);
+	list_del(&bridge->list);
+	module_put(bridge->driver->owner);
+}
+EXPORT_SYMBOL_GPL(agp_remove_bridge);
+
+int agp_off;
+int agp_try_unsupported_boot;
+EXPORT_SYMBOL(agp_off);
+EXPORT_SYMBOL(agp_try_unsupported_boot);
+
+#ifndef MODULE
+static __init int agp_setup(char *s)
+{
+	if (!strcmp(s,"off"))
+		agp_off = 1;
+	if (!strcmp(s,"try_unsupported"))
+		agp_try_unsupported_boot = 1;
+	return 1;
+}
+__setup("agp=", agp_setup);
+#endif
+
+MODULE_AUTHOR("Dave Jones, Jeff Hartmann");
+MODULE_DESCRIPTION("AGP GART driver");
+MODULE_LICENSE("GPL and additional rights");
+MODULE_ALIAS_MISCDEV(AGPGART_MINOR);