Hi, apologies if I am not posting to the appropriate list(s). I am using QEMU-KVM and try to implement a simple character device which offers mmap() functionality of host device memory to guest userspace. For this purpose, I have written a dummy guest driver which communicates with a qemu backend device. Specifically, the guest driver allocates a page and passes the associated address to qemu, which then translates it to host virtual address (cpu_physical_memory_map()). It then calls mmap() with MAP_FIXED and this host virtual address, which succeeds, and sends back the response. The problem arises here, when guest (either in kernespace or in userspace via remap_pfn_range()) tries to access the relevant address and faults with EPT. The path goes to handle_ept_violation() in kvm module and eventually BUG_ON() is triggered at: virt/kvm/kvm_main.c:1252 (version 3.16): -- cut here -- pfn = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; BUG_ON(!kvm_is_mmio_pfn(pfn)); -- cut here -- addr == vma->vm_start and pfn is assigned the value of vma->vm_pgoff !! What am I missing here? Is this scenario invalid? Can you please shed some light? Thanks in advance! --Stefanos
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