System information

• GPU: RTX 4090
• Driver: 566.36
• DXVK version: 2.5.3

Log files

err:   VUID-vkCmdFillBuffer-size-00027:
err:   Validation Error: [ VUID-vkCmdFillBuffer-size-00027 ] Object 0: handle = 0x1c8b4957140, type = VK_OBJECT_TYPE_COMMAND_BUFFER; Object 1: handle = 0x4e4775000000006e, name = Buffer (50), type = VK_OBJECT_TYPE_BUFFER; | MessageID = 0xdd944df9 | vkCmdFillBuffer(): size (37288) is greater than dstBuffer (VkBuffer 0x4e4775000000006e[Buffer (50)]) size (37286) minus dstOffset (0). The Vulkan spec states: If size is not equal to VK_WHOLE_SIZE, size must be less than or equal to the size of dstBuffer minus dstOffset (https://vulkan.lunarg.com/doc/view/1.3.275.0/windows/1.3-extensions/vkspec.html#VUID-vkCmdFillBuffer-size-00027)

Issue description

This validation error is caused by trying to clear a buffer with a non-multiple of 4 size (as a multiple of 4 is required by vkCmdFillBuffer) which happens in some games. Currently DXVK attempts to mitigate this by aligning the size to 4 here, but aligning upwards violates another requirement of vkCmdFillBuffer, specifically that the clear size must be smaller than the buffer size, leading to this validation error.

Unfortunately Vulkan seems to have no good way to clear a buffer like this with the fill command, even using VK_WHOLE_SIZE will only fill to the nearest smaller multiple of 4, leaving a few bytes at the end uncleared potentially. As such the best fix to this is probably to use alignDown instead of align to mimic the behavior of VK_WHOLE_SIZE and to eliminate this validation error. This buffer clearing seems to be only done for compatibility anyways (e.g. for games erroneously relying on buffers to be initialized with zeroed contents even though it's meant to be undefined), so missing clearing a few bytes at the end of the buffer probably isn't the end of the world, but maybe there's a better solution than this.