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, 118 insertions, 0 deletions

diff --git a/arch/m68k/mm/init.c b/arch/m68k/mm/init.c
new file mode 100644
index 000000000..3b88c0dd1
--- /dev/null
+++ b/arch/m68k/mm/init.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/arch/m68k/mm/init.c
+ *
+ *  Copyright (C) 1995  Hamish Macdonald
+ *
+ *  Contains common initialization routines, specific init code moved
+ *  to motorola.c and sun3mmu.c
+ */
+
+#include <linux/module.h>
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/memblock.h>
+#include <linux/gfp.h>
+
+#include <asm/setup.h>
+#include <linux/uaccess.h>
+#include <asm/page.h>
+#include <asm/pgalloc.h>
+#include <asm/traps.h>
+#include <asm/machdep.h>
+#include <asm/io.h>
+#ifdef CONFIG_ATARI
+#include <asm/atari_stram.h>
+#endif
+#include <asm/sections.h>
+#include <asm/tlb.h>
+
+void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
+{
+	max_zone_pfns[ZONE_DMA] = PFN_DOWN(memblock_end_of_DRAM());
+}
+
+#ifdef CONFIG_MMU
+
+int m68k_virt_to_node_shift;
+
+void __init m68k_setup_node(int node)
+{
+	node_set_online(node);
+}
+
+#else /* CONFIG_MMU */
+
+/*
+ * paging_init() continues the virtual memory environment setup which
+ * was begun by the code in arch/head.S.
+ * The parameters are pointers to where to stick the starting and ending
+ * addresses of available kernel virtual memory.
+ */
+void __init paging_init(void)
+{
+	/*
+	 * Make sure start_mem is page aligned, otherwise bootmem and
+	 * page_alloc get different views of the world.
+	 */
+	unsigned long end_mem = memory_end & PAGE_MASK;
+
+	high_memory = (void *) end_mem;
+}
+
+#endif /* CONFIG_MMU */
+
+void free_initmem(void)
+{
+#ifndef CONFIG_MMU_SUN3
+	free_initmem_default(-1);
+#endif /* CONFIG_MMU_SUN3 */
+}
+
+#if defined(CONFIG_MMU) && !defined(CONFIG_COLDFIRE)
+#define VECTORS	&vectors[0]
+#else
+#define VECTORS	_ramvec
+#endif
+
+static inline void init_pointer_tables(void)
+{
+#if defined(CONFIG_MMU) && !defined(CONFIG_SUN3) && !defined(CONFIG_COLDFIRE)
+	int i, j;
+
+	/* insert pointer tables allocated so far into the tablelist */
+	init_pointer_table(kernel_pg_dir, TABLE_PGD);
+	for (i = 0; i < PTRS_PER_PGD; i++) {
+		pud_t *pud = (pud_t *)&kernel_pg_dir[i];
+		pmd_t *pmd_dir;
+
+		if (!pud_present(*pud))
+			continue;
+
+		pmd_dir = (pmd_t *)pgd_page_vaddr(kernel_pg_dir[i]);
+		init_pointer_table(pmd_dir, TABLE_PMD);
+
+		for (j = 0; j < PTRS_PER_PMD; j++) {
+			pmd_t *pmd = &pmd_dir[j];
+			pte_t *pte_dir;
+
+			if (!pmd_present(*pmd))
+				continue;
+
+			pte_dir = (pte_t *)pmd_page_vaddr(*pmd);
+			init_pointer_table(pte_dir, TABLE_PTE);
+		}
+	}
+#endif
+}
+
+void __init mem_init(void)
+{
+	init_pointer_tables();
+}