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, 88 insertions, 0 deletions

diff --git a/arch/powerpc/boot/ebony.c b/arch/powerpc/boot/ebony.c
new file mode 100644
index 000000000..add2316d3
--- /dev/null
+++ b/arch/powerpc/boot/ebony.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2007 David Gibson, IBM Corporation.
+ *
+ * Based on earlier code:
+ *   Copyright (C) Paul Mackerras 1997.
+ *
+ *   Matt Porter <mporter@kernel.crashing.org>
+ *   Copyright 2002-2005 MontaVista Software Inc.
+ *
+ *   Eugene Surovegin <eugene.surovegin@zultys.com> or <ebs@ebshome.net>
+ *   Copyright (c) 2003, 2004 Zultys Technologies
+ */
+#include <stdarg.h>
+#include <stddef.h>
+#include "types.h"
+#include "elf.h"
+#include "string.h"
+#include "stdio.h"
+#include "page.h"
+#include "ops.h"
+#include "reg.h"
+#include "io.h"
+#include "dcr.h"
+#include "4xx.h"
+#include "44x.h"
+
+static u8 *ebony_mac0, *ebony_mac1;
+
+#define EBONY_FPGA_PATH		"/plb/opb/ebc/fpga"
+#define	EBONY_FPGA_FLASH_SEL	0x01
+#define EBONY_SMALL_FLASH_PATH	"/plb/opb/ebc/small-flash"
+
+static void ebony_flashsel_fixup(void)
+{
+	void *devp;
+	u32 reg[3] = {0x0, 0x0, 0x80000};
+	u8 *fpga;
+	u8 fpga_reg0 = 0x0;
+
+	devp = finddevice(EBONY_FPGA_PATH);
+	if (!devp)
+		fatal("Couldn't locate FPGA node %s\n\r", EBONY_FPGA_PATH);
+
+	if (getprop(devp, "virtual-reg", &fpga, sizeof(fpga)) != sizeof(fpga))
+		fatal("%s has missing or invalid virtual-reg property\n\r",
+		      EBONY_FPGA_PATH);
+
+	fpga_reg0 = in_8(fpga);
+
+	devp = finddevice(EBONY_SMALL_FLASH_PATH);
+	if (!devp)
+		fatal("Couldn't locate small flash node %s\n\r",
+		      EBONY_SMALL_FLASH_PATH);
+
+	if (getprop(devp, "reg", reg, sizeof(reg)) != sizeof(reg))
+		fatal("%s has reg property of unexpected size\n\r",
+		      EBONY_SMALL_FLASH_PATH);
+
+	/* Invert address bit 14 (IBM-endian) if FLASH_SEL fpga bit is set */
+	if (fpga_reg0 & EBONY_FPGA_FLASH_SEL)
+		reg[1] ^= 0x80000;
+
+	setprop(devp, "reg", reg, sizeof(reg));
+}
+
+static void ebony_fixups(void)
+{
+	// FIXME: sysclk should be derived by reading the FPGA registers
+	unsigned long sysclk = 33000000;
+
+	ibm440gp_fixup_clocks(sysclk, 6 * 1843200);
+	ibm4xx_sdram_fixup_memsize();
+	dt_fixup_mac_address_by_alias("ethernet0", ebony_mac0);
+	dt_fixup_mac_address_by_alias("ethernet1", ebony_mac1);
+	ibm4xx_fixup_ebc_ranges("/plb/opb/ebc");
+	ebony_flashsel_fixup();
+}
+
+void ebony_init(void *mac0, void *mac1)
+{
+	platform_ops.fixups = ebony_fixups;
+	platform_ops.exit = ibm44x_dbcr_reset;
+	ebony_mac0 = mac0;
+	ebony_mac1 = mac1;
+	fdt_init(_dtb_start);
+	serial_console_init();
+}