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

From: "Huang, Kai" <kai.huang@intel.com>
To: "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
	"Chatre, Reinette" <reinette.chatre@intel.com>,
	"jarkko@kernel.org" <jarkko@kernel.org>,
	"Dhanraj, Vijay" <vijay.dhanraj@intel.com>,
	"haitao.huang@linux.intel.com" <haitao.huang@linux.intel.com>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>
Subject: Re: [RFC PATCH v4 2/4] x86/sgx: Implement support for MADV_WILLNEED
Date: Tue, 14 Feb 2023 09:47:24 +0000	[thread overview]
Message-ID: <3c7b4f7bf3e7c2a213662b1c9fdaa979050a9327.camel@intel.com> (raw)
In-Reply-To: <20230128045529.15749-3-haitao.huang@linux.intel.com>

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?