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, 115 insertions, 0 deletions

diff --git a/sound/soc/sof/nocodec.c b/sound/soc/sof/nocodec.c
new file mode 100644
index 000000000..34744f8ae
--- /dev/null
+++ b/sound/soc/sof/nocodec.c
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+//
+// This file is provided under a dual BSD/GPLv2 license.  When using or
+// redistributing this file, you may do so under either license.
+//
+// Copyright(c) 2018 Intel Corporation
+//
+// Author: Liam Girdwood <liam.r.girdwood@linux.intel.com>
+//
+
+#include <linux/module.h>
+#include <sound/sof.h>
+#include "sof-audio.h"
+#include "sof-priv.h"
+
+static struct snd_soc_card sof_nocodec_card = {
+	.name = "nocodec", /* the sof- prefix is added by the core */
+	.owner = THIS_MODULE
+};
+
+static int sof_nocodec_bes_setup(struct device *dev,
+				 struct snd_soc_dai_driver *drv,
+				 struct snd_soc_dai_link *links,
+				 int link_num)
+{
+	struct snd_soc_card *card = &sof_nocodec_card;
+	struct snd_soc_dai_link_component *dlc;
+	int i;
+
+	if (!drv || !links)
+		return -EINVAL;
+
+	/* set up BE dai_links */
+	for (i = 0; i < link_num; i++) {
+		dlc = devm_kcalloc(dev, 2, sizeof(*dlc), GFP_KERNEL);
+		if (!dlc)
+			return -ENOMEM;
+
+		links[i].name = devm_kasprintf(dev, GFP_KERNEL,
+					       "NoCodec-%d", i);
+		if (!links[i].name)
+			return -ENOMEM;
+
+		links[i].stream_name = links[i].name;
+
+		links[i].cpus = &dlc[0];
+		links[i].codecs = &snd_soc_dummy_dlc;
+		links[i].platforms = &dlc[1];
+
+		links[i].num_cpus = 1;
+		links[i].num_codecs = 1;
+		links[i].num_platforms = 1;
+
+		links[i].id = i;
+		links[i].no_pcm = 1;
+		links[i].cpus->dai_name = drv[i].name;
+		links[i].platforms->name = dev_name(dev->parent);
+
+		links[i].playback_only =  drv[i].playback.channels_min && !drv[i].capture.channels_min;
+		links[i].capture_only  = !drv[i].playback.channels_min &&  drv[i].capture.channels_min;
+
+		links[i].be_hw_params_fixup = sof_pcm_dai_link_fixup;
+	}
+
+	card->dai_link = links;
+	card->num_links = link_num;
+
+	return 0;
+}
+
+static int sof_nocodec_setup(struct device *dev, struct snd_soc_acpi_mach *mach)
+{
+	u32 num_dai_drivers = mach->mach_params.num_dai_drivers;
+	struct snd_soc_dai_driver *dai_drivers = mach->mach_params.dai_drivers;
+	struct snd_soc_dai_link *links;
+
+	/* create dummy BE dai_links */
+	links = devm_kcalloc(dev, num_dai_drivers, sizeof(struct snd_soc_dai_link), GFP_KERNEL);
+	if (!links)
+		return -ENOMEM;
+
+	return sof_nocodec_bes_setup(dev, dai_drivers, links, num_dai_drivers);
+}
+
+static int sof_nocodec_probe(struct platform_device *pdev)
+{
+	struct snd_soc_card *card = &sof_nocodec_card;
+	struct snd_soc_acpi_mach *mach;
+	int ret;
+
+	card->dev = &pdev->dev;
+	mach = pdev->dev.platform_data;
+
+	snd_soc_card_set_topology_name(card, "sof");
+
+	ret = sof_nocodec_setup(card->dev, mach);
+	if (ret < 0)
+		return ret;
+
+	return devm_snd_soc_register_card(&pdev->dev, card);
+}
+
+static struct platform_driver sof_nocodec_audio = {
+	.probe = sof_nocodec_probe,
+	.driver = {
+		.name = "sof-nocodec",
+		.pm = &snd_soc_pm_ops,
+	},
+};
+module_platform_driver(sof_nocodec_audio)
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_DESCRIPTION("ASoC sof nocodec");
+MODULE_AUTHOR("Liam Girdwood");
+MODULE_ALIAS("platform:sof-nocodec");