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, 110 insertions, 0 deletions

diff --git a/drivers/clk/imx/clk-cpu.c b/drivers/clk/imx/clk-cpu.c
new file mode 100644
index 000000000..f53dbaacd
--- /dev/null
+++ b/drivers/clk/imx/clk-cpu.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2014 Lucas Stach <l.stach@pengutronix.de>, Pengutronix
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/export.h>
+#include <linux/slab.h>
+#include "clk.h"
+
+struct clk_cpu {
+	struct clk_hw	hw;
+	struct clk	*div;
+	struct clk	*mux;
+	struct clk	*pll;
+	struct clk	*step;
+};
+
+static inline struct clk_cpu *to_clk_cpu(struct clk_hw *hw)
+{
+	return container_of(hw, struct clk_cpu, hw);
+}
+
+static unsigned long clk_cpu_recalc_rate(struct clk_hw *hw,
+					 unsigned long parent_rate)
+{
+	struct clk_cpu *cpu = to_clk_cpu(hw);
+
+	return clk_get_rate(cpu->div);
+}
+
+static int clk_cpu_determine_rate(struct clk_hw *hw,
+				  struct clk_rate_request *req)
+{
+	struct clk_cpu *cpu = to_clk_cpu(hw);
+
+	req->rate = clk_round_rate(cpu->pll, req->rate);
+
+	return 0;
+}
+
+static int clk_cpu_set_rate(struct clk_hw *hw, unsigned long rate,
+			    unsigned long parent_rate)
+{
+	struct clk_cpu *cpu = to_clk_cpu(hw);
+	int ret;
+
+	/* switch to PLL bypass clock */
+	ret = clk_set_parent(cpu->mux, cpu->step);
+	if (ret)
+		return ret;
+
+	/* reprogram PLL */
+	ret = clk_set_rate(cpu->pll, rate);
+	if (ret) {
+		clk_set_parent(cpu->mux, cpu->pll);
+		return ret;
+	}
+	/* switch back to PLL clock */
+	clk_set_parent(cpu->mux, cpu->pll);
+
+	/* Ensure the divider is what we expect */
+	clk_set_rate(cpu->div, rate);
+
+	return 0;
+}
+
+static const struct clk_ops clk_cpu_ops = {
+	.recalc_rate	= clk_cpu_recalc_rate,
+	.determine_rate = clk_cpu_determine_rate,
+	.set_rate	= clk_cpu_set_rate,
+};
+
+struct clk_hw *imx_clk_hw_cpu(const char *name, const char *parent_name,
+		struct clk *div, struct clk *mux, struct clk *pll,
+		struct clk *step)
+{
+	struct clk_cpu *cpu;
+	struct clk_hw *hw;
+	struct clk_init_data init;
+	int ret;
+
+	cpu = kzalloc_obj(*cpu);
+	if (!cpu)
+		return ERR_PTR(-ENOMEM);
+
+	cpu->div = div;
+	cpu->mux = mux;
+	cpu->pll = pll;
+	cpu->step = step;
+
+	init.name = name;
+	init.ops = &clk_cpu_ops;
+	init.flags = CLK_IS_CRITICAL;
+	init.parent_names = &parent_name;
+	init.num_parents = 1;
+
+	cpu->hw.init = &init;
+	hw = &cpu->hw;
+
+	ret = clk_hw_register(NULL, hw);
+	if (ret) {
+		kfree(cpu);
+		return ERR_PTR(ret);
+	}
+
+	return hw;
+}
+EXPORT_SYMBOL_GPL(imx_clk_hw_cpu);