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, 444 insertions, 0 deletions

diff --git a/scripts/make_fit.py b/scripts/make_fit.py
new file mode 100755
index 000000000..15ba26974
--- /dev/null
+++ b/scripts/make_fit.py
@@ -0,0 +1,444 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright 2024 Google LLC
+# Written by Simon Glass <sjg@chromium.org>
+#
+
+"""Build a FIT containing a lot of devicetree files
+
+Usage:
+    make_fit.py -A arm64 -n 'Linux-6.6' -O linux
+        -o arch/arm64/boot/image.fit -k /tmp/kern/arch/arm64/boot/image.itk
+        -r /boot/initrd.img-6.14.0-27-generic @arch/arm64/boot/dts/dtbs-list
+        -E -c gzip
+
+Creates a FIT containing the supplied kernel, an optional ramdisk, and a set of
+devicetree files, either specified individually or listed in a file (with an
+'@' prefix).
+
+Use -r to specify an existing ramdisk/initrd file.
+
+Use -E to generate an external FIT (where the data is placed after the
+FIT data structure). This allows parsing of the data without loading
+the entire FIT.
+
+Use -c to compress the data, using bzip2, gzip, lz4, lzma, lzo and
+zstd algorithms.
+
+Use -D to decompose "composite" DTBs into their base components and
+deduplicate the resulting base DTBs and DTB overlays. This requires the
+DTBs to be sourced from the kernel build directory, as the implementation
+looks at the .cmd files produced by the kernel build.
+
+The resulting FIT can be booted by bootloaders which support FIT, such
+as U-Boot, Linuxboot, Tianocore, etc.
+"""
+
+import argparse
+import collections
+import multiprocessing
+import os
+import subprocess
+import sys
+import tempfile
+import time
+
+import libfdt
+
+
+# Tool extension and the name of the command-line tools
+CompTool = collections.namedtuple('CompTool', 'ext,tools')
+
+COMP_TOOLS = {
+    'bzip2': CompTool('.bz2', 'pbzip2,bzip2'),
+    'gzip': CompTool('.gz', 'pigz,gzip'),
+    'lz4': CompTool('.lz4', 'lz4'),
+    'lzma': CompTool('.lzma', 'lzma'),
+    'lzo': CompTool('.lzo', 'lzop'),
+    'xz': CompTool('.xz', 'xz'),
+    'zstd': CompTool('.zstd', 'zstd'),
+}
+
+
+def parse_args():
+    """Parse the program ArgumentParser
+
+    Returns:
+        Namespace object containing the arguments
+    """
+    epilog = 'Build a FIT from a directory tree containing .dtb files'
+    parser = argparse.ArgumentParser(epilog=epilog, fromfile_prefix_chars='@')
+    parser.add_argument('-A', '--arch', type=str, required=True,
+          help='Specifies the architecture')
+    parser.add_argument('-c', '--compress', type=str, default='none',
+          help='Specifies the compression')
+    parser.add_argument('-D', '--decompose-dtbs', action='store_true',
+          help='Decompose composite DTBs into base DTB and overlays')
+    parser.add_argument('-E', '--external', action='store_true',
+          help='Convert the FIT to use external data')
+    parser.add_argument('-n', '--name', type=str, required=True,
+          help='Specifies the name')
+    parser.add_argument('-o', '--output', type=str, required=True,
+          help='Specifies the output file (.fit)')
+    parser.add_argument('-O', '--os', type=str, required=True,
+          help='Specifies the operating system')
+    parser.add_argument('-k', '--kernel', type=str, required=True,
+          help='Specifies the (uncompressed) kernel input file (.itk)')
+    parser.add_argument('-r', '--ramdisk', type=str,
+          help='Specifies the ramdisk/initrd input file')
+    parser.add_argument('-v', '--verbose', action='store_true',
+                        help='Enable verbose output')
+    parser.add_argument('dtbs', type=str, nargs='*',
+          help='Specifies the devicetree files to process')
+
+    return parser.parse_args()
+
+
+def setup_fit(fsw, name):
+    """Make a start on writing the FIT
+
+    Outputs the root properties and the 'images' node
+
+    Args:
+        fsw (libfdt.FdtSw): Object to use for writing
+        name (str): Name of kernel image
+    """
+    fsw.INC_SIZE = 16 << 20
+    fsw.finish_reservemap()
+    fsw.begin_node('')
+    fsw.property_string('description', f'{name} with devicetree set')
+    fsw.property_u32('#address-cells', 1)
+
+    fsw.property_u32('timestamp', int(time.time()))
+    fsw.begin_node('images')
+
+
+def write_kernel(fsw, data, args):
+    """Write out the kernel image
+
+    Writes a kernel node along with the required properties
+
+    Args:
+        fsw (libfdt.FdtSw): Object to use for writing
+        data (bytes): Data to write (possibly compressed)
+        args (Namespace): Contains necessary strings:
+            arch: FIT architecture, e.g. 'arm64'
+            fit_os: Operating Systems, e.g. 'linux'
+            name: Name of OS, e.g. 'Linux-6.6.0-rc7'
+            compress: Compression algorithm to use, e.g. 'gzip'
+    """
+    with fsw.add_node('kernel'):
+        fsw.property_string('description', args.name)
+        fsw.property_string('type', 'kernel_noload')
+        fsw.property_string('arch', args.arch)
+        fsw.property_string('os', args.os)
+        fsw.property_string('compression', args.compress)
+        fsw.property('data', data)
+        fsw.property_u32('load', 0)
+        fsw.property_u32('entry', 0)
+
+
+def write_ramdisk(fsw, data, args):
+    """Write out the ramdisk image
+
+    Writes a ramdisk node along with the required properties
+
+    Args:
+        fsw (libfdt.FdtSw): Object to use for writing
+        data (bytes): Data to write (possibly compressed)
+        args (Namespace): Contains necessary strings:
+            arch: FIT architecture, e.g. 'arm64'
+            fit_os: Operating Systems, e.g. 'linux'
+    """
+    with fsw.add_node('ramdisk'):
+        fsw.property_string('description', 'Ramdisk')
+        fsw.property_string('type', 'ramdisk')
+        fsw.property_string('arch', args.arch)
+        fsw.property_string('compression', 'none')
+        fsw.property_string('os', args.os)
+        fsw.property('data', data)
+
+
+def finish_fit(fsw, entries, has_ramdisk=False):
+    """Finish the FIT ready for use
+
+    Writes the /configurations node and subnodes
+
+    Args:
+        fsw (libfdt.FdtSw): Object to use for writing
+        entries (list of tuple): List of configurations:
+            str: Description of model
+            str: Compatible stringlist
+        has_ramdisk (bool): True if a ramdisk is included in the FIT
+    """
+    fsw.end_node()
+    seq = 0
+    with fsw.add_node('configurations'):
+        for model, compat, files in entries:
+            seq += 1
+            with fsw.add_node(f'conf-{seq}'):
+                fsw.property('compatible', bytes(compat))
+                fsw.property_string('description', model)
+                fsw.property('fdt', bytes(''.join(f'fdt-{x}\x00' for x in files), "ascii"))
+                fsw.property_string('kernel', 'kernel')
+                if has_ramdisk:
+                    fsw.property_string('ramdisk', 'ramdisk')
+    fsw.end_node()
+
+
+def compress_data(inf, compress):
+    """Compress data using a selected algorithm
+
+    Args:
+        inf (IOBase): Filename containing the data to compress
+        compress (str): Compression algorithm, e.g. 'gzip'
+
+    Return:
+        bytes: Compressed data
+    """
+    if compress == 'none':
+        return inf.read()
+
+    comp = COMP_TOOLS.get(compress)
+    if not comp:
+        raise ValueError(f"Unknown compression algorithm '{compress}'")
+
+    with tempfile.NamedTemporaryFile() as comp_fname:
+        with open(comp_fname.name, 'wb') as outf:
+            done = False
+            for tool in comp.tools.split(','):
+                try:
+                    # Add parallel flags for tools that support them
+                    cmd = [tool]
+                    if tool in ('zstd', 'xz'):
+                        cmd.extend(['-T0'])  # Use all available cores
+                    cmd.append('-c')
+                    subprocess.call(cmd, stdin=inf, stdout=outf)
+                    done = True
+                    break
+                except FileNotFoundError:
+                    pass
+            if not done:
+                raise ValueError(f'Missing tool(s): {comp.tools}\n')
+            with open(comp_fname.name, 'rb') as compf:
+                comp_data = compf.read()
+    return comp_data
+
+
+def compress_dtb(fname, compress):
+    """Compress a single DTB file
+
+    Args:
+        fname (str): Filename containing the DTB
+        compress (str): Compression algorithm, e.g. 'gzip'
+
+    Returns:
+        tuple: (str: fname, bytes: compressed_data)
+    """
+    with open(fname, 'rb') as inf:
+        compressed = compress_data(inf, compress)
+    return fname, compressed
+
+
+def output_dtb(fsw, seq, fname, arch, compress, data=None):
+    """Write out a single devicetree to the FIT
+
+    Args:
+        fsw (libfdt.FdtSw): Object to use for writing
+        seq (int): Sequence number (1 for first)
+        fname (str): Filename containing the DTB
+        arch (str): FIT architecture, e.g. 'arm64'
+        compress (str): Compressed algorithm, e.g. 'gzip'
+        data (bytes): Pre-compressed data (optional)
+    """
+    with fsw.add_node(f'fdt-{seq}'):
+        fsw.property_string('description', os.path.basename(fname))
+        fsw.property_string('type', 'flat_dt')
+        fsw.property_string('arch', arch)
+        fsw.property_string('compression', compress)
+
+        if data is None:
+            with open(fname, 'rb') as inf:
+                data = compress_data(inf, compress)
+        fsw.property('data', data)
+
+
+def process_dtb(fname, args):
+    """Process an input DTB, decomposing it if requested and is possible
+
+    Args:
+        fname (str): Filename containing the DTB
+        args (Namespace): Program arguments
+    Returns:
+        tuple:
+            str: Model name string
+            str: Root compatible string
+            files: list of filenames corresponding to the DTB
+    """
+    # Get the compatible / model information
+    with open(fname, 'rb') as inf:
+        data = inf.read()
+    fdt = libfdt.FdtRo(data)
+    model = fdt.getprop(0, 'model').as_str()
+    compat = fdt.getprop(0, 'compatible')
+
+    if args.decompose_dtbs:
+        # Check if the DTB needs to be decomposed
+        path, basename = os.path.split(fname)
+        cmd_fname = os.path.join(path, f'.{basename}.cmd')
+        with open(cmd_fname, 'r', encoding='ascii') as inf:
+            cmd = inf.read()
+
+        if 'scripts/dtc/fdtoverlay' in cmd:
+            # This depends on the structure of the composite DTB command
+            files = cmd.split()
+            files = files[files.index('-i') + 1:]
+        else:
+            files = [fname]
+    else:
+        files = [fname]
+
+    return (model, compat, files)
+
+
+def _process_dtbs(args, fsw, entries, fdts):
+    """Process all DTB files and add them to the FIT
+
+    Args:
+        args: Program arguments
+        fsw: FIT writer object
+        entries: List to append entries to
+        fdts: Dictionary of processed DTBs
+
+    Returns:
+        tuple:
+            Number of files processed
+            Total size of files processed
+    """
+    seq = 0
+    size = 0
+
+    # First figure out the unique DTB files that need compression
+    todo = []
+    file_info = []  # List of (fname, model, compat, files) tuples
+
+    for fname in args.dtbs:
+        # Ignore non-DTB (*.dtb) files
+        if os.path.splitext(fname)[1] != '.dtb':
+            continue
+
+        try:
+            (model, compat, files) = process_dtb(fname, args)
+        except Exception as e:
+            sys.stderr.write(f'Error processing {fname}:\n')
+            raise e
+
+        file_info.append((fname, model, compat, files))
+        for fn in files:
+            if fn not in fdts and fn not in todo:
+                todo.append(fn)
+
+    # Compress all DTBs in parallel
+    cache = {}
+    if todo and args.compress != 'none':
+        if args.verbose:
+            print(f'Compressing {len(todo)} DTBs...')
+
+        with multiprocessing.Pool() as pool:
+            compress_args = [(fn, args.compress) for fn in todo]
+            # unpacks each tuple, calls compress_dtb(fn, compress) in parallel
+            results = pool.starmap(compress_dtb, compress_args)
+
+        cache = dict(results)
+
+    # Now write all DTBs to the FIT using pre-compressed data
+    for fname, model, compat, files in file_info:
+        for fn in files:
+            if fn not in fdts:
+                seq += 1
+                size += os.path.getsize(fn)
+                output_dtb(fsw, seq, fn, args.arch, args.compress,
+                           cache.get(fn))
+                fdts[fn] = seq
+
+        files_seq = [fdts[fn] for fn in files]
+        entries.append([model, compat, files_seq])
+
+    return seq, size
+
+
+def build_fit(args):
+    """Build the FIT from the provided files and arguments
+
+    Args:
+        args (Namespace): Program arguments
+
+    Returns:
+        tuple:
+            bytes: FIT data
+            int: Number of configurations generated
+            size: Total uncompressed size of data
+    """
+    size = 0
+    fsw = libfdt.FdtSw()
+    setup_fit(fsw, args.name)
+    entries = []
+    fdts = {}
+
+    # Handle the kernel
+    with open(args.kernel, 'rb') as inf:
+        comp_data = compress_data(inf, args.compress)
+    size += os.path.getsize(args.kernel)
+    write_kernel(fsw, comp_data, args)
+
+    # Handle the ramdisk if provided. Compression is not supported as it is
+    # already compressed.
+    if args.ramdisk:
+        with open(args.ramdisk, 'rb') as inf:
+            data = inf.read()
+        size += len(data)
+        write_ramdisk(fsw, data, args)
+
+    count, fdt_size = _process_dtbs(args, fsw, entries, fdts)
+    size += fdt_size
+
+    finish_fit(fsw, entries, bool(args.ramdisk))
+
+    # Include the kernel itself in the returned file count
+    fdt = fsw.as_fdt()
+    fdt.pack()
+    return fdt.as_bytearray(), count + 1 + bool(args.ramdisk), size
+
+
+def run_make_fit():
+    """Run the tool's main logic"""
+    args = parse_args()
+
+    out_data, count, size = build_fit(args)
+    with open(args.output, 'wb') as outf:
+        outf.write(out_data)
+
+    ext_fit_size = None
+    if args.external:
+        mkimage = os.environ.get('MKIMAGE', 'mkimage')
+        subprocess.check_call([mkimage, '-E', '-F', args.output],
+                              stdout=subprocess.DEVNULL)
+
+        with open(args.output, 'rb') as inf:
+            data = inf.read()
+        ext_fit = libfdt.FdtRo(data)
+        ext_fit_size = ext_fit.totalsize()
+
+    if args.verbose:
+        comp_size = len(out_data)
+        print(f'FIT size {comp_size:#x}/{comp_size / 1024 / 1024:.1f} MB',
+              end='')
+        if ext_fit_size:
+            print(f', header {ext_fit_size:#x}/{ext_fit_size / 1024:.1f} KB',
+                  end='')
+        print(f', {count} files, uncompressed {size / 1024 / 1024:.1f} MB')
+
+
+if __name__ == "__main__":
+    sys.exit(run_make_fit())