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Registered Extension Number

58

Revision

1

Extension and Version Dependencies

Deprecation state

Other Extension Metadata

Last Modified Date

2016-08-19

IP Status

No known IP claims.

Contributors
  • James Jones, NVIDIA

  • Carsten Rohde, NVIDIA

Description

Applications may wish to export memory to other Vulkan instances or other APIs, or import memory from other Vulkan instances or other APIs to enable Vulkan workloads to be split up across application module, process, or API boundaries. This extension enables win32 applications to export win32 handles from Vulkan memory objects such that the underlying resources can be referenced outside the Vulkan instance that created them, and import win32 handles created in the Direct3D API to Vulkan memory objects.

New Enum Constants

  • VK_NV_EXTERNAL_MEMORY_WIN32_EXTENSION_NAME

  • VK_NV_EXTERNAL_MEMORY_WIN32_SPEC_VERSION

  • Extending VkStructureType:

    • VK_STRUCTURE_TYPE_EXPORT_MEMORY_WIN32_HANDLE_INFO_NV

    • VK_STRUCTURE_TYPE_IMPORT_MEMORY_WIN32_HANDLE_INFO_NV

Issues

1) If memory objects are shared between processes and APIs, is this considered aliasing according to the rules outlined in the Memory Aliasing section?

RESOLVED: Yes, but strict exceptions to the rules are added to allow some forms of aliasing in these cases. Further, other extensions may build upon these new aliasing rules to define specific support usage within Vulkan for imported native memory objects, or memory objects from other APIs.

2) Are new image layouts or metadata required to specify image layouts and layout transitions compatible with non-Vulkan APIs, or with other instances of the same Vulkan driver?

RESOLVED: No. Separate instances of the same Vulkan driver running on the same GPU should have identical internal layout semantics, so applictions have the tools they need to ensure views of images are consistent between the two instances. Other APIs will fall into two categories: Those that are Vulkan compatible (a term to be defined by subsequent interopability extensions), or Vulkan incompatible. When sharing images with Vulkan incompatible APIs, the Vulkan image must be transitioned to the VK_IMAGE_LAYOUT_GENERAL layout before handing it off to the external API.

Note this does not attempt to address cross-device transitions, nor transitions to engines on the same device which are not visible within the Vulkan API. Both of these are beyond the scope of this extension.

3) Do applications need to call CloseHandle() on the values returned from vkGetMemoryWin32HandleNV when handleType is VK_EXTERNAL_MEMORY_HANDLE_TYPE_OPAQUE_WIN32_BIT_NV?

RESOLVED: Yes, unless it is passed back in to another driver instance to import the object. A successful get call transfers ownership of the handle to the application, while an import transfers ownership to the associated driver. Destroying the memory object will not destroy the handle or the handle’s reference to the underlying memory resource.

Examples

    //
    // Create an exportable memory object and export an external
    // handle from it.
    //

    // Pick an external format and handle type.
    static const VkFormat format = VK_FORMAT_R8G8B8A8_UNORM;
    static const VkExternalMemoryHandleTypeFlagsNV handleType =
        VK_EXTERNAL_MEMORY_HANDLE_TYPE_OPAQUE_WIN32_BIT_NV;

    extern VkPhysicalDevice physicalDevice;
    extern VkDevice device;

    VkPhysicalDeviceMemoryProperties memoryProperties;
    VkExternalImageFormatPropertiesNV properties;
    VkExternalMemoryImageCreateInfoNV externalMemoryImageCreateInfo;
    VkDedicatedAllocationImageCreateInfoNV dedicatedImageCreateInfo;
    VkImageCreateInfo imageCreateInfo;
    VkImage image;
    VkMemoryRequirements imageMemoryRequirements;
    uint32_t numMemoryTypes;
    uint32_t memoryType;
    VkExportMemoryAllocateInfoNV exportMemoryAllocateInfo;
    VkDedicatedAllocationMemoryAllocateInfoNV dedicatedAllocationInfo;
    VkMemoryAllocateInfo memoryAllocateInfo;
    VkDeviceMemory memory;
    VkResult result;
    HANDLE memoryHnd;

    // Figure out how many memory types the device supports
    vkGetPhysicalDeviceMemoryProperties(physicalDevice,
                                        &memoryProperties);
    numMemoryTypes = memoryProperties.memoryTypeCount;

    // Check the external handle type capabilities for the chosen format
    // Exportable 2D image support with at least 1 mip level, 1 array
    // layer, and VK_SAMPLE_COUNT_1_BIT using optimal tiling and supporting
    // texturing and color rendering is required.
    result = vkGetPhysicalDeviceExternalImageFormatPropertiesNV(
        physicalDevice,
        format,
        VK_IMAGE_TYPE_2D,
        VK_IMAGE_TILING_OPTIMAL,
        VK_IMAGE_USAGE_SAMPLED_BIT |
        VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT,
        0,
        handleType,
        &properties);

    if ((result != VK_SUCCESS) ||
        !(properties.externalMemoryFeatures &
          VK_EXTERNAL_MEMORY_FEATURE_EXPORTABLE_BIT_NV)) {
        abort();
    }

    // Set up the external memory image creation info
    memset(&externalMemoryImageCreateInfo,
           0, sizeof(externalMemoryImageCreateInfo));
    externalMemoryImageCreateInfo.sType =
        VK_STRUCTURE_TYPE_EXTERNAL_MEMORY_IMAGE_CREATE_INFO_NV;
    externalMemoryImageCreateInfo.handleTypes = handleType;
    if (properties.externalMemoryFeatures &
        VK_EXTERNAL_MEMORY_FEATURE_DEDICATED_ONLY_BIT_NV) {
        memset(&dedicatedImageCreateInfo, 0, sizeof(dedicatedImageCreateInfo));
        dedicatedImageCreateInfo.sType =
            VK_STRUCTURE_TYPE_DEDICATED_ALLOCATION_IMAGE_CREATE_INFO_NV;
        dedicatedImageCreateInfo.dedicatedAllocation = VK_TRUE;
        externalMemoryImageCreateInfo.pNext = &dedicatedImageCreateInfo;
    }
    // Set up the  core image creation info
    memset(&imageCreateInfo, 0, sizeof(imageCreateInfo));
    imageCreateInfo.sType = VK_STRUCTURE_TYPE_IMAGE_CREATE_INFO;
    imageCreateInfo.pNext = &externalMemoryImageCreateInfo;
    imageCreateInfo.format = format;
    imageCreateInfo.extent.width = 64;
    imageCreateInfo.extent.height = 64;
    imageCreateInfo.extent.depth = 1;
    imageCreateInfo.mipLevels = 1;
    imageCreateInfo.arrayLayers = 1;
    imageCreateInfo.samples = VK_SAMPLE_COUNT_1_BIT;
    imageCreateInfo.tiling = VK_IMAGE_TILING_OPTIMAL;
    imageCreateInfo.usage = VK_IMAGE_USAGE_SAMPLED_BIT |
        VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT;
    imageCreateInfo.sharingMode = VK_SHARING_MODE_EXCLUSIVE;
    imageCreateInfo.initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;

    vkCreateImage(device, &imageCreateInfo, NULL, &image);

    vkGetImageMemoryRequirements(device,
                                 image,
                                 &imageMemoryRequirements);

    // For simplicity, just pick the first compatible memory type.
    for (memoryType = 0; memoryType < numMemoryTypes; memoryType++) {
        if ((1 << memoryType) & imageMemoryRequirements.memoryTypeBits) {
            break;
        }
    }

    // At least one memory type must be supported given the prior external
    // handle capability check.
    assert(memoryType < numMemoryTypes);

    // Allocate the external memory object.
    memset(&exportMemoryAllocateInfo, 0, sizeof(exportMemoryAllocateInfo));
    exportMemoryAllocateInfo.sType =
        VK_STRUCTURE_TYPE_EXPORT_MEMORY_ALLOCATE_INFO_NV;
    exportMemoryAllocateInfo.handleTypes = handleType;
    if (properties.externalMemoryFeatures &
        VK_EXTERNAL_MEMORY_FEATURE_DEDICATED_ONLY_BIT_NV) {
        memset(&dedicatedAllocationInfo, 0, sizeof(dedicatedAllocationInfo));
        dedicatedAllocationInfo.sType =
            VK_STRUCTURE_TYPE_DEDICATED_ALLOCATION_MEMORY_ALLOCATE_INFO_NV;
        dedicatedAllocationInfo.image = image;
        exportMemoryAllocateInfo.pNext = &dedicatedAllocationInfo;
    }
    memset(&memoryAllocateInfo, 0, sizeof(memoryAllocateInfo));
    memoryAllocateInfo.sType = VK_STRUCTURE_TYPE_MEMORY_ALLOCATE_INFO;
    memoryAllocateInfo.pNext = &exportMemoryAllocateInfo;
    memoryAllocateInfo.allocationSize = imageMemoryRequirements.size;
    memoryAllocateInfo.memoryTypeIndex = memoryType;

    vkAllocateMemory(device, &memoryAllocateInfo, NULL, &memory);

    if (!(properties.externalMemoryFeatures &
          VK_EXTERNAL_MEMORY_FEATURE_DEDICATED_ONLY_BIT_NV)) {
        vkBindImageMemory(device, image, memory, 0);
    }

    // Get the external memory opaque FD handle
    vkGetMemoryWin32HandleNV(device, memory, &memoryHnd);

Version History

  • Revision 1, 2016-08-11 (James Jones)

    • Initial draft

See Also

Document Notes

For more information, see the Vulkan Specification

This page is a generated document. Fixes and changes should be made to the generator scripts, not directly.

Copyright (c) 2014-2020 Khronos Group. This work is licensed under a Creative Commons Attribution 4.0 International License.