Is it a bug that callingfromHost without vkFlushMappedMemoryRanges

[jcao-ai]

Hi, I was trying to understand how vulkan works from your src code.

When I looked into file: deviceArray.hpp in branch: vuh2,

auto fromHost(It1 begin, It2 end)-> void {
    if(Base::isHostVisible()){
        std::copy(begin, end, host_data());
        Base::_dev.unmapMemory(Base::_mem);
    } else { // memory is not host visible, use staging buffer
        auto stage_buf = HostArray<T, AllocDevice<properties::HostCoherent>>(Base::_dev, begin, end);
        copyBuf(Base::_dev, stage_buf, *this, size_bytes());
    }
}

What I think is that even if isHostVisible() return true, we should check whether the memory buffer underlied includes a flag: VK_MEMORY_PROPERTY_HOST_COHERENT_BIT, or we should call vkFlushMappedMemoryRanges and vkInvalidateMappedMemoryRanges .

This is a note from here

Unmapping non-coherent memory does not implicitly flush the host mapped memory, and host writes that have not been flushed may not ever be visible to the device. However, implementations must ensure that writes that have not been flushed do not become visible to any other memory.

Please correct me if I am wrong, thanks anyway!

[Glavnokoman]

I guess you are right. Will you create an MR?

[jcao-ai]

Sure, be glad to contribute to vuh. But still I am kind of newbie on Vulkan, try my best.