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, 248 insertions, 0 deletions

diff --git a/arch/powerpc/boot/addnote.c b/arch/powerpc/boot/addnote.c
new file mode 100644
index 000000000..787049274
--- /dev/null
+++ b/arch/powerpc/boot/addnote.c
@@ -0,0 +1,248 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Program to hack in a PT_NOTE program header entry in an ELF file.
+ * This is needed for OF on RS/6000s to load an image correctly.
+ * Note that OF needs a program header entry for the note, not an
+ * ELF section.
+ *
+ * Copyright 2000 Paul Mackerras.
+ *
+ * Adapted for 64 bit little endian images by Andrew Tauferner.
+ *
+ * Usage: addnote zImage
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+
+/* CHRP note section */
+static const char arch[] = "PowerPC";
+
+#define N_DESCR	6
+unsigned int descr[N_DESCR] = {
+	0xffffffff,		/* real-mode = true */
+	0x02000000,		/* real-base, i.e. where we expect OF to be */
+	0xffffffff,		/* real-size */
+	0xffffffff,		/* virt-base */
+	0xffffffff,		/* virt-size */
+	0x4000,			/* load-base */
+};
+
+/* RPA note section */
+static const char rpaname[] = "IBM,RPA-Client-Config";
+
+/*
+ * Note: setting ignore_my_client_config *should* mean that OF ignores
+ * all the other fields, but there is a firmware bug which means that
+ * it looks at the splpar field at least.  So these values need to be
+ * reasonable.
+ */
+#define N_RPA_DESCR	8
+unsigned int rpanote[N_RPA_DESCR] = {
+	0,			/* lparaffinity */
+	64,			/* min_rmo_size */
+	0,			/* min_rmo_percent */
+	40,			/* max_pft_size */
+	1,			/* splpar */
+	-1,			/* min_load */
+	0,			/* new_mem_def */
+	1,			/* ignore_my_client_config */
+};
+
+#define ROUNDUP(len)	(((len) + 3) & ~3)
+
+unsigned char buf[1024];
+#define ELFDATA2LSB     1
+#define ELFDATA2MSB     2
+static int e_data = ELFDATA2MSB;
+#define ELFCLASS32      1
+#define ELFCLASS64      2
+static int e_class = ELFCLASS32;
+
+#define GET_16BE(off)	((buf[off] << 8) + (buf[(off)+1]))
+#define GET_32BE(off)	((GET_16BE(off) << 16U) + GET_16BE((off)+2U))
+#define GET_64BE(off)	((((unsigned long long)GET_32BE(off)) << 32ULL) + \
+			((unsigned long long)GET_32BE((off)+4ULL)))
+#define PUT_16BE(off, v)(buf[off] = ((v) >> 8) & 0xff, \
+			 buf[(off) + 1] = (v) & 0xff)
+#define PUT_32BE(off, v)(PUT_16BE((off), (v) >> 16L), PUT_16BE((off) + 2, (v)))
+#define PUT_64BE(off, v)((PUT_32BE((off), (unsigned long long)(v) >> 32L), \
+			  PUT_32BE((off) + 4, (unsigned long long)(v))))
+
+#define GET_16LE(off)	((buf[off]) + (buf[(off)+1] << 8))
+#define GET_32LE(off)	(GET_16LE(off) + (GET_16LE((off)+2U) << 16U))
+#define GET_64LE(off)	((unsigned long long)GET_32LE(off) + \
+			(((unsigned long long)GET_32LE((off)+4ULL)) << 32ULL))
+#define PUT_16LE(off, v) (buf[off] = (v) & 0xff, \
+			  buf[(off) + 1] = ((v) >> 8) & 0xff)
+#define PUT_32LE(off, v) (PUT_16LE((off), (v)), PUT_16LE((off) + 2, (v) >> 16L))
+#define PUT_64LE(off, v) (PUT_32LE((off), (unsigned long long)(v)), \
+			  PUT_32LE((off) + 4, (unsigned long long)(v) >> 32L))
+
+#define GET_16(off)	(e_data == ELFDATA2MSB ? GET_16BE(off) : GET_16LE(off))
+#define GET_32(off)	(e_data == ELFDATA2MSB ? GET_32BE(off) : GET_32LE(off))
+#define GET_64(off)	(e_data == ELFDATA2MSB ? GET_64BE(off) : GET_64LE(off))
+#define PUT_16(off, v)	(e_data == ELFDATA2MSB ? PUT_16BE(off, v) : \
+			 PUT_16LE(off, v))
+#define PUT_32(off, v)  (e_data == ELFDATA2MSB ? PUT_32BE(off, v) : \
+			 PUT_32LE(off, v))
+#define PUT_64(off, v)  (e_data == ELFDATA2MSB ? PUT_64BE(off, v) : \
+			 PUT_64LE(off, v))
+
+/* Structure of an ELF file */
+#define E_IDENT		0	/* ELF header */
+#define	E_PHOFF		(e_class == ELFCLASS32 ? 28 : 32)
+#define E_PHENTSIZE	(e_class == ELFCLASS32 ? 42 : 54)
+#define E_PHNUM		(e_class == ELFCLASS32 ? 44 : 56)
+#define E_HSIZE		(e_class == ELFCLASS32 ? 52 : 64)
+
+#define EI_MAGIC	0	/* offsets in E_IDENT area */
+#define EI_CLASS	4
+#define EI_DATA		5
+
+#define PH_TYPE		0	/* ELF program header */
+#define PH_OFFSET	(e_class == ELFCLASS32 ? 4 : 8)
+#define PH_FILESZ	(e_class == ELFCLASS32 ? 16 : 32)
+#define PH_HSIZE	(e_class == ELFCLASS32 ? 32 : 56)
+
+#define PT_NOTE		4	/* Program header type = note */
+
+
+unsigned char elf_magic[4] = { 0x7f, 'E', 'L', 'F' };
+
+int
+main(int ac, char **av)
+{
+	int fd, n, i;
+	unsigned long ph, ps, np;
+	long nnote, nnote2, ns;
+
+	if (ac != 2) {
+		fprintf(stderr, "Usage: %s elf-file\n", av[0]);
+		exit(1);
+	}
+	fd = open(av[1], O_RDWR);
+	if (fd < 0) {
+		perror(av[1]);
+		exit(1);
+	}
+
+	nnote = 12 + ROUNDUP(strlen(arch) + 1) + sizeof(descr);
+	nnote2 = 12 + ROUNDUP(strlen(rpaname) + 1) + sizeof(rpanote);
+
+	n = read(fd, buf, sizeof(buf));
+	if (n < 0) {
+		perror("read");
+		exit(1);
+	}
+
+	if (memcmp(&buf[E_IDENT+EI_MAGIC], elf_magic, 4) != 0)
+		goto notelf;
+	e_class = buf[E_IDENT+EI_CLASS];
+	if (e_class != ELFCLASS32 && e_class != ELFCLASS64)
+		goto notelf;
+	e_data = buf[E_IDENT+EI_DATA];
+	if (e_data != ELFDATA2MSB && e_data != ELFDATA2LSB)
+		goto notelf;
+	if (n < E_HSIZE)
+		goto notelf;
+
+	ph = (e_class == ELFCLASS32 ? GET_32(E_PHOFF) : GET_64(E_PHOFF));
+	ps = GET_16(E_PHENTSIZE);
+	np = GET_16(E_PHNUM);
+	if (ph < E_HSIZE || ps < PH_HSIZE || np < 1)
+		goto notelf;
+	if (ph + (np + 2) * ps + nnote + nnote2 > n)
+		goto nospace;
+
+	for (i = 0; i < np; ++i) {
+		if (GET_32(ph + PH_TYPE) == PT_NOTE) {
+			fprintf(stderr, "%s already has a note entry\n",
+				av[1]);
+			exit(0);
+		}
+		ph += ps;
+	}
+
+	/* XXX check that the area we want to use is all zeroes */
+	for (i = 0; i < 2 * ps + nnote + nnote2; ++i)
+		if (buf[ph + i] != 0)
+			goto nospace;
+
+	/* fill in the program header entry */
+	ns = ph + 2 * ps;
+	PUT_32(ph + PH_TYPE, PT_NOTE);
+	if (e_class == ELFCLASS32)
+		PUT_32(ph + PH_OFFSET, ns);
+	else
+		PUT_64(ph + PH_OFFSET, ns);
+
+	if (e_class == ELFCLASS32)
+		PUT_32(ph + PH_FILESZ, nnote);
+	else
+		PUT_64(ph + PH_FILESZ, nnote);
+
+	/* fill in the note area we point to */
+	/* XXX we should probably make this a proper section */
+	PUT_32(ns, strlen(arch) + 1);
+	PUT_32(ns + 4, N_DESCR * 4);
+	PUT_32(ns + 8, 0x1275);
+	strcpy((char *) &buf[ns + 12], arch);
+	ns += 12 + strlen(arch) + 1;
+	for (i = 0; i < N_DESCR; ++i, ns += 4)
+		PUT_32BE(ns, descr[i]);
+
+	/* fill in the second program header entry and the RPA note area */
+	ph += ps;
+	PUT_32(ph + PH_TYPE, PT_NOTE);
+	if (e_class == ELFCLASS32)
+		PUT_32(ph + PH_OFFSET, ns);
+	else
+		PUT_64(ph + PH_OFFSET, ns);
+
+	if (e_class == ELFCLASS32)
+		PUT_32(ph + PH_FILESZ, nnote);
+	else
+		PUT_64(ph + PH_FILESZ, nnote2);
+
+	/* fill in the note area we point to */
+	PUT_32(ns, strlen(rpaname) + 1);
+	PUT_32(ns + 4, sizeof(rpanote));
+	PUT_32(ns + 8, 0x12759999);
+	strcpy((char *) &buf[ns + 12], rpaname);
+	ns += 12 + ROUNDUP(strlen(rpaname) + 1);
+	for (i = 0; i < N_RPA_DESCR; ++i, ns += 4)
+		PUT_32BE(ns, rpanote[i]);
+
+	/* Update the number of program headers */
+	PUT_16(E_PHNUM, np + 2);
+
+	/* write back */
+	i = lseek(fd, (long) 0, SEEK_SET);
+	if (i < 0) {
+		perror("lseek");
+		exit(1);
+	}
+	i = write(fd, buf, n);
+	if (i < 0) {
+		perror("write");
+		exit(1);
+	}
+	if (i < n) {
+		fprintf(stderr, "%s: write truncated\n", av[1]);
+		exit(1);
+	}
+
+	exit(0);
+
+ notelf:
+	fprintf(stderr, "%s does not appear to be an ELF file\n", av[1]);
+	exit(1);
+
+ nospace:
+	fprintf(stderr, "sorry, I can't find space in %s to put the note\n",
+		av[1]);
+	exit(1);
+}