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, 154 insertions, 0 deletions

diff --git a/arch/m68k/coldfire/nettel.c b/arch/m68k/coldfire/nettel.c
new file mode 100644
index 000000000..e304571e0
--- /dev/null
+++ b/arch/m68k/coldfire/nettel.c
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0
+/***************************************************************************/
+
+/*
+ *	nettel.c -- startup code support for the NETtel boards
+ *
+ *	Copyright (C) 2009, Greg Ungerer (gerg@snapgear.com)
+ */
+
+/***************************************************************************/
+
+#include <linux/kernel.h>
+#include <linux/param.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <asm/coldfire.h>
+#include <asm/mcfsim.h>
+#include <asm/nettel.h>
+
+/***************************************************************************/
+
+/*
+ * Define the IO and interrupt resources of the 2 SMC9196 interfaces.
+ */
+#define	NETTEL_SMC0_ADDR	0x30600300
+#define	NETTEL_SMC0_IRQ		29
+
+#define	NETTEL_SMC1_ADDR	0x30600000
+#define	NETTEL_SMC1_IRQ		27
+
+/*
+ * We need some access into the SMC9196 registers. Define those registers
+ * we will need here (including the smc91x.h doesn't seem to give us these
+ * in a simple form).
+ */
+#define	SMC91xx_BANKSELECT	14
+#define	SMC91xx_BASEADDR	2
+#define	SMC91xx_BASEMAC		4
+
+/***************************************************************************/
+
+static struct resource nettel_smc91x_0_resources[] = {
+	{
+		.start		= NETTEL_SMC0_ADDR,
+		.end		= NETTEL_SMC0_ADDR + 0x20,
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		.start		= NETTEL_SMC0_IRQ,
+		.end		= NETTEL_SMC0_IRQ,
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct resource nettel_smc91x_1_resources[] = {
+	{
+		.start		= NETTEL_SMC1_ADDR,
+		.end		= NETTEL_SMC1_ADDR + 0x20,
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		.start		= NETTEL_SMC1_IRQ,
+		.end		= NETTEL_SMC1_IRQ,
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct platform_device nettel_smc91x[] = {
+	{
+		.name			= "smc91x",
+		.id			= 0,
+		.num_resources		= ARRAY_SIZE(nettel_smc91x_0_resources),
+		.resource		= nettel_smc91x_0_resources,
+	},
+	{
+		.name			= "smc91x",
+		.id			= 1,
+		.num_resources		= ARRAY_SIZE(nettel_smc91x_1_resources),
+		.resource		= nettel_smc91x_1_resources,
+	},
+};
+
+static struct platform_device *nettel_devices[] __initdata = {
+	&nettel_smc91x[0],
+	&nettel_smc91x[1],
+};
+
+/***************************************************************************/
+
+static u8 nettel_macdefault[] __initdata = {
+	0x00, 0xd0, 0xcf, 0x00, 0x00, 0x01,
+};
+
+/*
+ * Set flash contained MAC address into SMC9196 core. Make sure the flash
+ * MAC address is sane, and not an empty flash. If no good use the Moreton
+ * Bay default MAC address instead.
+ */
+
+static void __init nettel_smc91x_setmac(unsigned int ioaddr, unsigned int flashaddr)
+{
+	u16 *macp;
+
+	macp = (u16 *) flashaddr;
+	if ((macp[0] == 0xffff) && (macp[1] == 0xffff) && (macp[2] == 0xffff))
+		macp = (u16 *) &nettel_macdefault[0];
+
+	mcf_write16(1, NETTEL_SMC0_ADDR + SMC91xx_BANKSELECT);
+	mcf_write16(macp[0], ioaddr + SMC91xx_BASEMAC);
+	mcf_write16(macp[1], ioaddr + SMC91xx_BASEMAC + 2);
+	mcf_write16(macp[2], ioaddr + SMC91xx_BASEMAC + 4);
+}
+
+/***************************************************************************/
+
+/*
+ * Re-map the address space of at least one of the SMC ethernet
+ * parts. Both parts power up decoding the same address, so we
+ * need to move one of them first, before doing anything else.
+ */
+
+static void __init nettel_smc91x_init(void)
+{
+	mcf_write16(0x00ec, MCFSIM_PADDR);
+	mcf_setppdata(0, 0x0080);
+	mcf_write16(1, NETTEL_SMC0_ADDR + SMC91xx_BANKSELECT);
+	mcf_write16(0x0067, NETTEL_SMC0_ADDR + SMC91xx_BASEADDR);
+	mcf_setppdata(0x0080, 0);
+
+	/* Set correct chip select timing for SMC9196 accesses */
+	mcf_write16(0x1180, MCFSIM_CSCR3);
+
+	/* Set the SMC interrupts to be auto-vectored */
+	mcf_autovector(NETTEL_SMC0_IRQ);
+	mcf_autovector(NETTEL_SMC1_IRQ);
+
+	/* Set MAC addresses from flash for both interfaces */
+	nettel_smc91x_setmac(NETTEL_SMC0_ADDR, 0xf0006000);
+	nettel_smc91x_setmac(NETTEL_SMC1_ADDR, 0xf0006006);
+}
+
+/***************************************************************************/
+
+static int __init init_nettel(void)
+{
+	nettel_smc91x_init();
+	platform_add_devices(nettel_devices, ARRAY_SIZE(nettel_devices));
+	return 0;
+}
+
+arch_initcall(init_nettel);
+
+/***************************************************************************/