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, 93 insertions, 0 deletions

diff --git a/arch/powerpc/boot/of.c b/arch/powerpc/boot/of.c
new file mode 100644
index 000000000..2fbd4ae60
--- /dev/null
+++ b/arch/powerpc/boot/of.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) Paul Mackerras 1997.
+ */
+#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 "of.h"
+
+/* Value picked to match that used by yaboot */
+#define PROG_START	0x01400000	/* only used on 64-bit systems */
+#define RAM_END		(512<<20)	/* Fixme: use OF */
+#define	ONE_MB		0x100000
+
+
+
+static unsigned long claim_base;
+
+void epapr_platform_init(unsigned long r3, unsigned long r4, unsigned long r5,
+			 unsigned long r6, unsigned long r7);
+
+static void *of_try_claim(unsigned long size)
+{
+	unsigned long addr = 0;
+
+	if (claim_base == 0)
+		claim_base = _ALIGN_UP((unsigned long)_end, ONE_MB);
+
+	for(; claim_base < RAM_END; claim_base += ONE_MB) {
+#ifdef DEBUG
+		printf("    trying: 0x%08lx\n\r", claim_base);
+#endif
+		addr = (unsigned long) of_claim(claim_base, size, 0);
+		if (addr != PROM_ERROR)
+			break;
+	}
+	if (addr == 0)
+		return NULL;
+	claim_base = PAGE_ALIGN(claim_base + size);
+	return (void *)addr;
+}
+
+static void of_image_hdr(const void *hdr)
+{
+	const Elf64_Ehdr *elf64 = hdr;
+
+	if (elf64->e_ident[EI_CLASS] == ELFCLASS64) {
+		/*
+		 * Maintain a "magic" minimum address. This keeps some older
+		 * firmware platforms running.
+		 */
+		if (claim_base < PROG_START)
+			claim_base = PROG_START;
+	}
+}
+
+static void of_platform_init(unsigned long a1, unsigned long a2, void *promptr)
+{
+	platform_ops.image_hdr = of_image_hdr;
+	platform_ops.malloc = of_try_claim;
+	platform_ops.exit = of_exit;
+	platform_ops.vmlinux_alloc = of_vmlinux_alloc;
+
+	dt_ops.finddevice = of_finddevice;
+	dt_ops.getprop = of_getprop;
+	dt_ops.setprop = of_setprop;
+
+	of_console_init();
+
+	of_init(promptr);
+	loader_info.promptr = promptr;
+	if (a1 && a2 && a2 != 0xdeadbeef) {
+		loader_info.initrd_addr = a1;
+		loader_info.initrd_size = a2;
+	}
+}
+
+void platform_init(unsigned long r3, unsigned long r4, unsigned long r5,
+		   unsigned long r6, unsigned long r7)
+{
+	/* Detect OF vs. ePAPR boot */
+	if (r5)
+		of_platform_init(r3, r4, (void *)r5);
+	else
+		epapr_platform_init(r3, r4, r5, r6, r7);
+}
+