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, 105 insertions, 0 deletions

diff --git a/sound/soc/soc-devres.c b/sound/soc/soc-devres.c
new file mode 100644
index 000000000..718165ba8
--- /dev/null
+++ b/sound/soc/soc-devres.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// soc-devres.c  --  ALSA SoC Audio Layer devres functions
+//
+// Copyright (C) 2013 Linaro Ltd
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <sound/soc.h>
+#include <sound/dmaengine_pcm.h>
+
+static void devm_component_release(struct device *dev, void *res)
+{
+	const struct snd_soc_component_driver **cmpnt_drv = res;
+
+	snd_soc_unregister_component_by_driver(dev, *cmpnt_drv);
+}
+
+/**
+ * devm_snd_soc_register_component - resource managed component registration
+ * @dev: Device used to manage component
+ * @cmpnt_drv: Component driver
+ * @dai_drv: DAI driver
+ * @num_dai: Number of DAIs to register
+ *
+ * Register a component with automatic unregistration when the device is
+ * unregistered.
+ */
+int devm_snd_soc_register_component(struct device *dev,
+			 const struct snd_soc_component_driver *cmpnt_drv,
+			 struct snd_soc_dai_driver *dai_drv, int num_dai)
+{
+	const struct snd_soc_component_driver **ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_component_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = snd_soc_register_component(dev, cmpnt_drv, dai_drv, num_dai);
+	if (ret == 0) {
+		*ptr = cmpnt_drv;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(devm_snd_soc_register_component);
+
+/**
+ * devm_snd_soc_register_card - resource managed card registration
+ * @dev: Device used to manage card
+ * @card: Card to register
+ *
+ * Register a card with automatic unregistration when the device is
+ * unregistered.
+ */
+int devm_snd_soc_register_card(struct device *dev, struct snd_soc_card *card)
+{
+	card->devres_dev = dev;
+	return snd_soc_register_card(card);
+}
+EXPORT_SYMBOL_GPL(devm_snd_soc_register_card);
+
+#ifdef CONFIG_SND_SOC_GENERIC_DMAENGINE_PCM
+
+static void devm_dmaengine_pcm_release(struct device *dev, void *res)
+{
+	snd_dmaengine_pcm_unregister(*(struct device **)res);
+}
+
+/**
+ * devm_snd_dmaengine_pcm_register - resource managed dmaengine PCM registration
+ * @dev: The parent device for the PCM device
+ * @config: Platform specific PCM configuration
+ * @flags: Platform specific quirks
+ *
+ * Register a dmaengine based PCM device with automatic unregistration when the
+ * device is unregistered.
+ */
+int devm_snd_dmaengine_pcm_register(struct device *dev,
+	const struct snd_dmaengine_pcm_config *config, unsigned int flags)
+{
+	struct device **ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_dmaengine_pcm_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = snd_dmaengine_pcm_register(dev, config, flags);
+	if (ret == 0) {
+		*ptr = dev;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(devm_snd_dmaengine_pcm_register);
+
+#endif