sdk/banjo/fuchsia.sysmem/metadata.banjo

// Copyright 2021 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// fou0d in the LICENSE file.

library fuchsia.sysmem;

/// "SyM"
const uint32 SYSMEM_METADATA = 0x53794d64;  // 0x53794d00 | DEVICE_METADATA_PRIVATE

struct SysmemMetadata {
  uint32 vid;
  uint32 pid;

  // protected_memory_size
  // contiguous_memory_size
  //
  // Positive values are interpreted as bytes, and are aligned up to next
  // ZX_PAGE_SIZE.
  //
  // Negative values are interpreted as a percentage of physical memory (after
  // negation), and resulting size in bytes is aligned up to next ZX_PAGE_SIZE.

  // protected_memory_size
  //
  // Size of the protected memory pool.  See above for how this value is
  // interpreted.
  //
  // 0 means there is no protected memory pool.
  int64 protected_memory_size;

  // contiguous_memory_size
  //
  // Size of the pool used to allocate contiguous memory.  See above for how
  // this value is interpreted.
  //
  // Zero means no space is reserved up front, which will end up using
  // zx::vmo::create_contiguous() for each allocation instead of allocating up
  // front, which can be prone to failure when physical memory becomes
  // fragmented.
  //
  // There is no fallback from pre-reserved to zx::vmo::create_contiguous().
  // If we're pre-reserving memory, we should reserve enough.
  int64 contiguous_memory_size;
};