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Subject: Re: [PATCH v28 11/22] x86/sgx: Linux Enclave Driver
To:     Sean Christopherson <sean.j.christopherson@intel.com>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
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        Suresh Siddha <suresh.b.siddha@intel.com>,
        Haitao Huang <haitao.huang@linux.intel.com>,
        Chunyang Hui <sanqian.hcy@antfin.com>
References: <20200303233609.713348-1-jarkko.sakkinen@linux.intel.com>
 <20200303233609.713348-12-jarkko.sakkinen@linux.intel.com>
 <20200305174015.GJ11500@linux.intel.com>
From:   Jethro Beekman <jethro@fortanix.com>
Message-ID: <e445c2f8-fddd-5740-0e26-a03e023918bf@fortanix.com>
Date:   Thu, 5 Mar 2020 19:24:11 +0100
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On 2020-03-05 18:40, Sean Christopherson wrote:
> On Wed, Mar 04, 2020 at 01:35:58AM +0200, Jarkko Sakkinen wrote:
>> diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/a=
sm/sgx.h
>> new file mode 100644
>> index 000000000000..5edb08ab8fd0
>> --- /dev/null
>> +++ b/arch/x86/include/uapi/asm/sgx.h
>> @@ -0,0 +1,66 @@
>> +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) WITH Linux-sysc=
all-note */
>> +/*
>> + * Copyright(c) 2016-19 Intel Corporation.
>> + */
>> +#ifndef _UAPI_ASM_X86_SGX_H
>> +#define _UAPI_ASM_X86_SGX_H
>> +
>> +#include <linux/types.h>
>> +#include <linux/ioctl.h>
>> +
>> +/**
>> + * enum sgx_epage_flags - page control flags
>> + * %SGX_PAGE_MEASURE:	Measure the page contents with a sequence of
>> + *			ENCLS[EEXTEND] operations.
>> + */
>> +enum sgx_page_flags {
>> +	SGX_PAGE_MEASURE	=3D 0x01,
>> +};
>> +
>> +#define SGX_MAGIC 0xA4
>> +
>> +#define SGX_IOC_ENCLAVE_CREATE \
>> +	_IOW(SGX_MAGIC, 0x00, struct sgx_enclave_create)
>> +#define SGX_IOC_ENCLAVE_ADD_PAGES \
>> +	_IOWR(SGX_MAGIC, 0x01, struct sgx_enclave_add_pages)
>> +#define SGX_IOC_ENCLAVE_INIT \
>> +	_IOW(SGX_MAGIC, 0x02, struct sgx_enclave_init)
>> +
>> +/**
>> + * struct sgx_enclave_create - parameter structure for the
>> + *                             %SGX_IOC_ENCLAVE_CREATE ioctl
>> + * @src:	address for the SECS page data
>> + */
>> +struct sgx_enclave_create  {
>> +	__u64	src;
>=20
> Would it make sense to add reserved fields to the structs so that new
> features can be added in a backwards compatible way?  E.g. if we want t=
o
> allow userspace to control the backing store by passing in a file
> descriptor ENCLAVE_CREATE.

Reserving space for future fields is not necessary because the size of th=
e struct is encoded in the ioctl number. The kernel can use this to diffe=
rentiate between different call versions from userspace.

--
Jethro Beekman | Fortanix


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