Re: [RFC PATCH v4 2/4] x86/sgx: Implement support for MADV_WILLNEED

Huang, Kai
2023-02-14T09:48:11Z

On Fri, 2023-01-27 at 20:55 -0800, Haitao Huang wrote:
> @@ -97,10 +99,81 @@ static int sgx_mmap(struct file *file, struct vm_area_struct *vma)
>   vma->vm_ops = &sgx_vm_ops;
>   vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP | VM_IO;
>   vma->vm_private_data = encl;
> + vma->vm_pgoff = PFN_DOWN(vma->vm_start - encl->base);
>
>   return 0;
>  }

Perhaps I am missing something, but above change looks weird.

Conceptually, it doesn't/shouldn't belong to this series, which essentially
preallocates and does EAUG EPC pages for a (or part of) given enclave. The EAUG
logic should already be working for the normal fault path, which means the code
change above either: 1) has been done at other place; 2) isn't needed.

I have kinda forgotten the userspace sequence to create an enclave. If I recall
correctly, you do below to create an enclave:

1) encl_fd = open("/dev/sgx_enclave");
2) encl_addr = mmap(encl_fd, encl_size, 0 /* pgoff */);
3) IOCTL(ECREATE, encl_addr, encl_size);

Would the above code change break the "mmap()" in above step 2?