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, 99 insertions, 0 deletions

diff --git a/arch/powerpc/boot/pq2.c b/arch/powerpc/boot/pq2.c
new file mode 100644
index 000000000..de27f1c07
--- /dev/null
+++ b/arch/powerpc/boot/pq2.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * PowerQUICC II support functions
+ *
+ * Author: Scott Wood <scottwood@freescale.com>
+ *
+ * Copyright (c) 2007 Freescale Semiconductor, Inc.
+ */
+
+#include "ops.h"
+#include "types.h"
+#include "fsl-soc.h"
+#include "pq2.h"
+#include "stdio.h"
+#include "io.h"
+
+#define PQ2_SCCR (0x10c80/4) /* System Clock Configuration Register */
+#define PQ2_SCMR (0x10c88/4) /* System Clock Mode Register */
+
+static int pq2_corecnf_map[] = {
+	3, 2, 2, 2, 4, 4, 5, 9, 6, 11, 8, 10, 3, 12, 7, -1,
+	6, 5, 13, 2, 14, 4, 15, 9, 0, 11, 8, 10, 16, 12, 7, -1
+};
+
+/* Get various clocks from crystal frequency.
+ * Returns zero on failure and non-zero on success.
+ */
+int pq2_get_clocks(u32 crystal, u32 *sysfreq, u32 *corefreq,
+                   u32 *timebase, u32 *brgfreq)
+{
+	u32 *immr;
+	u32 sccr, scmr, mainclk, busclk;
+	int corecnf, busdf, plldf, pllmf, dfbrg;
+
+	immr = fsl_get_immr();
+	if (!immr) {
+		printf("pq2_get_clocks: Couldn't get IMMR base.\r\n");
+		return 0;
+	}
+
+	sccr = in_be32(&immr[PQ2_SCCR]);
+	scmr = in_be32(&immr[PQ2_SCMR]);
+
+	dfbrg = sccr & 3;
+	corecnf = (scmr >> 24) & 0x1f;
+	busdf = (scmr >> 20) & 0xf;
+	plldf = (scmr >> 12) & 1;
+	pllmf = scmr & 0xfff;
+
+	mainclk = crystal * (pllmf + 1) / (plldf + 1);
+	busclk = mainclk / (busdf + 1);
+
+	if (sysfreq)
+		*sysfreq = mainclk / 2;
+	if (timebase)
+		*timebase = busclk / 4;
+	if (brgfreq)
+		*brgfreq = mainclk / (1 << ((dfbrg + 1) * 2));
+
+	if (corefreq) {
+		int coremult = pq2_corecnf_map[corecnf];
+
+		if (coremult < 0)
+			*corefreq = mainclk / 2;
+		else if (coremult == 0)
+			return 0;
+		else
+			*corefreq = busclk * coremult / 2;
+	}
+
+	return 1;
+}
+
+/* Set common device tree fields based on the given clock frequencies. */
+void pq2_set_clocks(u32 sysfreq, u32 corefreq, u32 timebase, u32 brgfreq)
+{
+	void *node;
+
+	dt_fixup_cpu_clocks(corefreq, timebase, sysfreq);
+
+	node = finddevice("/soc/cpm");
+	if (node)
+		setprop(node, "clock-frequency", &sysfreq, 4);
+
+	node = finddevice("/soc/cpm/brg");
+	if (node)
+		setprop(node, "clock-frequency", &brgfreq, 4);
+}
+
+int pq2_fixup_clocks(u32 crystal)
+{
+	u32 sysfreq, corefreq, timebase, brgfreq;
+
+	if (!pq2_get_clocks(crystal, &sysfreq, &corefreq, &timebase, &brgfreq))
+		return 0;
+
+	pq2_set_clocks(sysfreq, corefreq, timebase, brgfreq);
+	return 1;
+}