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>

3 files changed, 81 insertions, 0 deletions

diff --git a/drivers/reset/tegra/Kconfig b/drivers/reset/tegra/Kconfig
new file mode 100644
index 000000000..4a2d26d12
--- /dev/null
+++ b/drivers/reset/tegra/Kconfig
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config RESET_TEGRA_BPMP
+	bool "Tegra BPMP Reset Driver" if COMPILE_TEST
+	default TEGRA_BPMP
diff --git a/drivers/reset/tegra/Makefile b/drivers/reset/tegra/Makefile
new file mode 100644
index 000000000..eccba896a
--- /dev/null
+++ b/drivers/reset/tegra/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_RESET_TEGRA_BPMP) += reset-bpmp.o
diff --git a/drivers/reset/tegra/reset-bpmp.c b/drivers/reset/tegra/reset-bpmp.c
new file mode 100644
index 000000000..4c5bba52b
--- /dev/null
+++ b/drivers/reset/tegra/reset-bpmp.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2016 NVIDIA Corporation
+ */
+
+#include <linux/reset-controller.h>
+
+#include <soc/tegra/bpmp.h>
+#include <soc/tegra/bpmp-abi.h>
+
+static struct tegra_bpmp *to_tegra_bpmp(struct reset_controller_dev *rstc)
+{
+	return container_of(rstc, struct tegra_bpmp, rstc);
+}
+
+static int tegra_bpmp_reset_common(struct reset_controller_dev *rstc,
+				   enum mrq_reset_commands command,
+				   unsigned int id)
+{
+	struct tegra_bpmp *bpmp = to_tegra_bpmp(rstc);
+	struct mrq_reset_request request;
+	struct tegra_bpmp_message msg;
+	int err;
+
+	memset(&request, 0, sizeof(request));
+	request.cmd = command;
+	request.reset_id = id;
+
+	memset(&msg, 0, sizeof(msg));
+	msg.mrq = MRQ_RESET;
+	msg.tx.data = &request;
+	msg.tx.size = sizeof(request);
+
+	err = tegra_bpmp_transfer(bpmp, &msg);
+	if (err)
+		return err;
+	if (msg.rx.ret)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int tegra_bpmp_reset_module(struct reset_controller_dev *rstc,
+				   unsigned long id)
+{
+	return tegra_bpmp_reset_common(rstc, CMD_RESET_MODULE, id);
+}
+
+static int tegra_bpmp_reset_assert(struct reset_controller_dev *rstc,
+				   unsigned long id)
+{
+	return tegra_bpmp_reset_common(rstc, CMD_RESET_ASSERT, id);
+}
+
+static int tegra_bpmp_reset_deassert(struct reset_controller_dev *rstc,
+				     unsigned long id)
+{
+	return tegra_bpmp_reset_common(rstc, CMD_RESET_DEASSERT, id);
+}
+
+static const struct reset_control_ops tegra_bpmp_reset_ops = {
+	.reset = tegra_bpmp_reset_module,
+	.assert = tegra_bpmp_reset_assert,
+	.deassert = tegra_bpmp_reset_deassert,
+};
+
+int tegra_bpmp_init_resets(struct tegra_bpmp *bpmp)
+{
+	bpmp->rstc.ops = &tegra_bpmp_reset_ops;
+	bpmp->rstc.owner = THIS_MODULE;
+	bpmp->rstc.of_node = bpmp->dev->of_node;
+	bpmp->rstc.nr_resets = bpmp->soc->num_resets;
+
+	return devm_reset_controller_register(bpmp->dev, &bpmp->rstc);
+}