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>

4 files changed, 173 insertions, 0 deletions

diff --git a/arch/mips/econet/Kconfig b/arch/mips/econet/Kconfig
new file mode 100644
index 000000000..579fb5b01
--- /dev/null
+++ b/arch/mips/econet/Kconfig
@@ -0,0 +1,48 @@
+# SPDX-License-Identifier: GPL-2.0
+if ECONET
+
+choice
+	prompt "EcoNet SoC selection"
+	default SOC_ECONET_EN751221
+	help
+	  Select EcoNet MIPS SoC type. Individual SoCs within a family are
+	  very similar, so is it enough to select the right family, and
+	  then customize to the specific SoC using the device tree only.
+
+	config SOC_ECONET_EN751221
+		bool "EN751221 family"
+		select COMMON_CLK
+		select ECONET_EN751221_INTC
+		select HAVE_PCI
+		select IRQ_MIPS_CPU
+		select PCI_DRIVERS_GENERIC
+		select SYS_SUPPORTS_MULTITHREADING
+		help
+		  The EN751221 family includes EN7512, RN7513, EN7521, EN7526.
+		  They are based on single core MIPS 34Kc processors. To boot
+		  this kernel, you will need a device tree such as
+		  MIPS_RAW_APPENDED_DTB=y, and a root filesystem.
+endchoice
+
+choice
+	prompt "Devicetree selection"
+	default DTB_ECONET_NONE
+	help
+	  Select the devicetree.
+
+	config DTB_ECONET_NONE
+		bool "None"
+
+	config DTB_ECONET_SMARTFIBER_XP8421_B
+		bool "EN751221 SmartFiber XP8421-B"
+		depends on SOC_ECONET_EN751221
+		select BUILTIN_DTB
+		help
+		  The SmartFiber XP8421-B is a device based on the EN751221 SoC.
+		  It has 512MB of memory and 256MB of NAND flash. This kernel
+		  needs only an appended initramfs to boot. It can be loaded
+		  through XMODEM and booted from memory in the bootloader, or
+		  it can be packed in tclinux.trx format and written to flash.
+endchoice
+
+endif
diff --git a/arch/mips/econet/Makefile b/arch/mips/econet/Makefile
new file mode 100644
index 000000000..7e4529e7d
--- /dev/null
+++ b/arch/mips/econet/Makefile
@@ -0,0 +1,2 @@
+
+obj-y := init.o
diff --git a/arch/mips/econet/Platform b/arch/mips/econet/Platform
new file mode 100644
index 000000000..ea5616447
--- /dev/null
+++ b/arch/mips/econet/Platform
@@ -0,0 +1,5 @@
+# To address a 7.2MB kernel size limit in the EcoNet SDK bootloader,
+# we put the load address well above where the bootloader loads and then use
+# zboot. So please set CONFIG_ZBOOT_LOAD_ADDRESS to the address where your
+# bootloader actually places the kernel.
+load-$(CONFIG_ECONET)	+= 0xffffffff81000000
diff --git a/arch/mips/econet/init.c b/arch/mips/econet/init.c
new file mode 100644
index 000000000..ae45b8788
--- /dev/null
+++ b/arch/mips/econet/init.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * EcoNet setup code
+ *
+ * Copyright (C) 2025 Caleb James DeLisle <cjd@cjdns.fr>
+ */
+
+#include <linux/init.h>
+#include <linux/of_clk.h>
+#include <linux/irqchip.h>
+
+#include <asm/addrspace.h>
+#include <asm/io.h>
+#include <asm/bootinfo.h>
+#include <asm/time.h>
+#include <asm/prom.h>
+#include <asm/smp-ops.h>
+#include <asm/reboot.h>
+
+#define CR_AHB_RSTCR		((void __iomem *)CKSEG1ADDR(0x1fb00040))
+#define RESET			BIT(31)
+
+#define UART_BASE		CKSEG1ADDR(0x1fbf0003)
+#define UART_REG_SHIFT		2
+
+static void hw_reset(char *command)
+{
+	iowrite32(RESET, CR_AHB_RSTCR);
+}
+
+/*
+ * vsmp_init_secondary expects either GIC or cascading interrupt configuration.
+ * The EN751221 is a 34Kc with VEIC, but not GIC compatible. The cascading
+ * configuration enables lines 6 and 7 for performance counters, but when this
+ * is done on the EN751221 intc with VEIC enabled, it causes the whole intc to
+ * stop sending interrupts.
+ * Only unmask lines 0 and 1 (software interrupts) in init_secondary.
+ */
+#ifdef CONFIG_MIPS_MT_SMP
+extern const struct plat_smp_ops vsmp_smp_ops;
+static struct plat_smp_ops en75_smp_ops __ro_after_init;
+
+static void en751221_init_secondary(void)
+{
+	write_c0_status((read_c0_status() & ~ST0_IM) |
+		(STATUSF_IP0 | STATUSF_IP1));
+}
+
+static int __init en751221_register_vsmp_smp_ops(void)
+{
+	if (!cpu_has_mipsmt)
+		return -ENODEV;
+
+	en75_smp_ops = vsmp_smp_ops;
+	en75_smp_ops.init_secondary = en751221_init_secondary;
+	register_smp_ops(&en75_smp_ops);
+	return 0;
+}
+#else
+static int __init en751221_register_vsmp_smp_ops(void)
+{
+	return -ENODEV;
+}
+#endif /* CONFIG_MIPS_MT_SMP */
+
+/* 1. Bring up early printk. */
+void __init prom_init(void)
+{
+	setup_8250_early_printk_port(UART_BASE, UART_REG_SHIFT, 0);
+	_machine_restart = hw_reset;
+}
+
+/* 2. Parse the DT and find memory */
+void __init plat_mem_setup(void)
+{
+	void *dtb;
+
+	set_io_port_base(KSEG1);
+
+	dtb = get_fdt();
+	if (!dtb)
+		panic("no dtb found");
+
+	__dt_setup_arch(dtb);
+
+	early_init_dt_scan_memory();
+}
+
+/* 3. Overload __weak device_tree_init(), add SMP ops */
+void __init device_tree_init(void)
+{
+	unflatten_and_copy_device_tree();
+
+	/* EN751221 dual-vpe */
+	if (!en751221_register_vsmp_smp_ops())
+		return;
+
+	/* EN751221 with MT_SMP disabled */
+	register_up_smp_ops();
+}
+
+const char *get_system_type(void)
+{
+	return "EcoNet-EN75xx";
+}
+
+/* 4. Initialize the IRQ subsystem */
+void __init arch_init_irq(void)
+{
+	irqchip_init();
+}
+
+/* 5. Timers */
+void __init plat_time_init(void)
+{
+	of_clk_init(NULL);
+	timer_probe();
+}