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Extension and Version Dependencies

• Requires Vulkan 1.0

• Requires VK_KHR_get_physical_device_properties2

Contact

2019-06-24

IP Status

No known IP claims.

Interactions and External Dependencies
Contributors
• Jeff Bolz, NVIDIA

• Neil Henning, AMD

• Tobias Hector, AMD

• Jason Ekstrand, Intel

• Baldur Karlsson, Valve

• Jan-Harald Fredriksen, Arm

Description

This extension allows the application to query a 64-bit buffer device address value for a buffer, which can be used to access the buffer memory via the PhysicalStorageBuffer storage class in the GL_EXT_buffer_reference GLSL extension and SPV_KHR_physical_storage_buffer SPIR-V extension.

Another way to describe this extension is that it adds “pointers to buffer memory in shaders”. By calling vkGetBufferDeviceAddress with a VkBuffer, it will return a VkDeviceAddress value which represents the address of the start of the buffer.

vkGetBufferOpaqueCaptureAddress and vkGetDeviceMemoryOpaqueCaptureAddress allow opaque addresses for buffers and memory objects to be queried for the current process. A trace capture and replay tool can then supply these addresses to be used at replay time to match the addresses used when the trace was captured. To enable tools to insert these queries, new memory allocation flags must be specified for memory objects that will be bound to buffers accessed via the PhysicalStorageBuffer storage class. Note that this mechanism is intended only to support capture/replay tools, and is not recommended for use in other applications.

There are various use cases this extension is designed for. It is required for ray tracing, useful for DX12 portability, and by allowing buffer addresses to be stored in memory it enables more complex data structures to be created.

This extension can also be used to hardcode a dedicated debug channel into all shaders by querying a pointer at startup and pushing that into shaders as a run-time constant (e.g. specialization constant) that avoids impacting other descriptor limits.

There are examples of usage in the GL_EXT_buffer_reference spec for how to use this in a high-level shading language such as GLSL. The GL_EXT_buffer_reference2 and GL_EXT_buffer_reference_uvec2 extensions were also added to help cover a few additional edge cases.

Promotion to Vulkan 1.2

All functionality in this extension is included in core Vulkan 1.2, with the KHR suffix omitted. However, if Vulkan 1.2 is supported and this extension is not, the bufferDeviceAddress capability is optional. The original type, enum and command names are still available as aliases of the core functionality.

New Enum Constants

• VK_KHR_BUFFER_DEVICE_ADDRESS_EXTENSION_NAME

• VK_KHR_BUFFER_DEVICE_ADDRESS_SPEC_VERSION

• Extending VkBufferCreateFlagBits:

• VK_BUFFER_CREATE_DEVICE_ADDRESS_CAPTURE_REPLAY_BIT_KHR

• Extending VkBufferUsageFlagBits:

• VK_BUFFER_USAGE_SHADER_DEVICE_ADDRESS_BIT_KHR

• Extending VkMemoryAllocateFlagBits:

• VK_MEMORY_ALLOCATE_DEVICE_ADDRESS_BIT_KHR

• VK_MEMORY_ALLOCATE_DEVICE_ADDRESS_CAPTURE_REPLAY_BIT_KHR

• Extending VkResult:

• VK_ERROR_INVALID_OPAQUE_CAPTURE_ADDRESS_KHR

• Extending VkStructureType:

• VK_STRUCTURE_TYPE_BUFFER_DEVICE_ADDRESS_INFO_KHR

• VK_STRUCTURE_TYPE_BUFFER_OPAQUE_CAPTURE_ADDRESS_CREATE_INFO_KHR

• VK_STRUCTURE_TYPE_DEVICE_MEMORY_OPAQUE_CAPTURE_ADDRESS_INFO_KHR

• VK_STRUCTURE_TYPE_MEMORY_OPAQUE_CAPTURE_ADDRESS_ALLOCATE_INFO_KHR

• VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_BUFFER_DEVICE_ADDRESS_FEATURES_KHR

Version History

• Revision 1, 2019-06-24 (Jan-Harald Fredriksen)

• Internal revisions based on VK_EXT_buffer_device_address

Examples

There are various use cases this extensions is designed for. It is required for ray tracing, useful for DX12 portability, and it allows storing buffer addresses in memory (enabling creating more complex data strcutures).

This extension can also be used to hardcode a dedicated debug channel into all shaders without impacting other descriptor limits by querying a buffer device address at startup and pushing that into shaders as a run-time constant (e.g. specialization constant).

There are examples of usage in the GL_EXT_buffer_reference spec for how to use this in a high-level shading language such as GLSL. The GL_EXT_buffer_reference2 and GL_EXT_buffer_reference_uvec2 extensions were added to help cover a few edge cases missed by the original GL_EXT_buffer_reference.

It is important to also be aware that the capture/replay mechanisms are meant for capture/replay tools, and should not be used general application usage.