Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: VuIu9B5BcaJplmARvlJJ5EJZJALZj5BrcMbqRX04vUfq2HNPXcy2aCmT3/lSK6d0NWSr4MmvWj
 Z2FVM5e/vZig==
IronPort-SDR: nNU0Y2JXTx2hhFNc/ONqjRo+sDHSf0le5k7suiST+i7vOlzqaa9gnFBHT0Ci2kpRorL5jSXnZG
 XpdVZOrUqPYA==
Subject: Re: [PATCH v41 05/24] x86/sgx: Initialize metadata for Enclave Page
 Cache (EPC) sections
To:     Hillf Danton <hdanton@sina.com>,
        Jarkko Sakkinen <jarkko@kernel.org>
Cc:     x86@kernel.org, linux-sgx@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Jethro Beekman <jethro@fortanix.com>,
        Serge Ayoun <serge.ayoun@intel.com>, akpm@linux-foundation.org
References: <20201112220135.165028-1-jarkko@kernel.org>
 <20201114084211.5284-1-hdanton@sina.com>
From:   Dave Hansen <dave.hansen@intel.com>
Autocrypt: addr=dave.hansen@intel.com; keydata=
 xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC
 oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY
 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb
 ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz
 VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W
 iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn
 c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1
 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb
 ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL
 QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzShEYXZpZCBDaHJp
 c3RvcGhlciBIYW5zZW4gPGRhdmVAc3I3MS5uZXQ+wsF7BBMBAgAlAhsDBgsJCAcDAgYVCAIJ
 CgsEFgIDAQIeAQIXgAUCTo3k0QIZAQAKCRBoNZUwcMmSsMO2D/421Xg8pimb9mPzM5N7khT0
 2MCnaGssU1T59YPE25kYdx2HntwdO0JA27Wn9xx5zYijOe6B21ufrvsyv42auCO85+oFJWfE
 K2R/IpLle09GDx5tcEmMAHX6KSxpHmGuJmUPibHVbfep2aCh9lKaDqQR07gXXWK5/yU1Dx0r
 VVFRaHTasp9fZ9AmY4K9/BSA3VkQ8v3OrxNty3OdsrmTTzO91YszpdbjjEFZK53zXy6tUD2d
 e1i0kBBS6NLAAsqEtneplz88T/v7MpLmpY30N9gQU3QyRC50jJ7LU9RazMjUQY1WohVsR56d
 ORqFxS8ChhyJs7BI34vQusYHDTp6PnZHUppb9WIzjeWlC7Jc8lSBDlEWodmqQQgp5+6AfhTD
 kDv1a+W5+ncq+Uo63WHRiCPuyt4di4/0zo28RVcjtzlGBZtmz2EIC3vUfmoZbO/Gn6EKbYAn
 rzz3iU/JWV8DwQ+sZSGu0HmvYMt6t5SmqWQo/hyHtA7uF5Wxtu1lCgolSQw4t49ZuOyOnQi5
 f8R3nE7lpVCSF1TT+h8kMvFPv3VG7KunyjHr3sEptYxQs4VRxqeirSuyBv1TyxT+LdTm6j4a
 mulOWf+YtFRAgIYyyN5YOepDEBv4LUM8Tz98lZiNMlFyRMNrsLV6Pv6SxhrMxbT6TNVS5D+6
 UorTLotDZKp5+M7BTQRUY85qARAAsgMW71BIXRgxjYNCYQ3Xs8k3TfAvQRbHccky50h99TUY
 sqdULbsb3KhmY29raw1bgmyM0a4DGS1YKN7qazCDsdQlxIJp9t2YYdBKXVRzPCCsfWe1dK/q
 66UVhRPP8EGZ4CmFYuPTxqGY+dGRInxCeap/xzbKdvmPm01Iw3YFjAE4PQ4hTMr/H76KoDbD
 cq62U50oKC83ca/PRRh2QqEqACvIH4BR7jueAZSPEDnzwxvVgzyeuhwqHY05QRK/wsKuhq7s
 UuYtmN92Fasbxbw2tbVLZfoidklikvZAmotg0dwcFTjSRGEg0Gr3p/xBzJWNavFZZ95Rj7Et
 db0lCt0HDSY5q4GMR+SrFbH+jzUY/ZqfGdZCBqo0cdPPp58krVgtIGR+ja2Mkva6ah94/oQN
 lnCOw3udS+Eb/aRcM6detZr7XOngvxsWolBrhwTQFT9D2NH6ryAuvKd6yyAFt3/e7r+HHtkU
 kOy27D7IpjngqP+b4EumELI/NxPgIqT69PQmo9IZaI/oRaKorYnDaZrMXViqDrFdD37XELwQ
 gmLoSm2VfbOYY7fap/AhPOgOYOSqg3/Nxcapv71yoBzRRxOc4FxmZ65mn+q3rEM27yRztBW9
 AnCKIc66T2i92HqXCw6AgoBJRjBkI3QnEkPgohQkZdAb8o9WGVKpfmZKbYBo4pEAEQEAAcLB
 XwQYAQIACQUCVGPOagIbDAAKCRBoNZUwcMmSsJeCEACCh7P/aaOLKWQxcnw47p4phIVR6pVL
 e4IEdR7Jf7ZL00s3vKSNT+nRqdl1ugJx9Ymsp8kXKMk9GSfmZpuMQB9c6io1qZc6nW/3TtvK
 pNGz7KPPtaDzvKA4S5tfrWPnDr7n15AU5vsIZvgMjU42gkbemkjJwP0B1RkifIK60yQqAAlT
 YZ14P0dIPdIPIlfEPiAWcg5BtLQU4Wg3cNQdpWrCJ1E3m/RIlXy/2Y3YOVVohfSy+4kvvYU3
 lXUdPb04UPw4VWwjcVZPg7cgR7Izion61bGHqVqURgSALt2yvHl7cr68NYoFkzbNsGsye9ft
 M9ozM23JSgMkRylPSXTeh5JIK9pz2+etco3AfLCKtaRVysjvpysukmWMTrx8QnI5Nn5MOlJj
 1Ov4/50JY9pXzgIDVSrgy6LYSMc4vKZ3QfCY7ipLRORyalFDF3j5AGCMRENJjHPD6O7bl3Xo
 4DzMID+8eucbXxKiNEbs21IqBZbbKdY1GkcEGTE7AnkA3Y6YB7I/j9mQ3hCgm5muJuhM/2Fr
 OPsw5tV/LmQ5GXH0JQ/TZXWygyRFyyI2FqNTx4WHqUn3yFj8rwTAU1tluRUYyeLy0ayUlKBH
 ybj0N71vWO936MqP6haFERzuPAIpxj2ezwu0xb1GjTk4ynna6h5GjnKgdfOWoRtoWndMZxbA
 z5cecg==
Message-ID: <0a96ecb7-50cc-634d-2f94-09e547be7b44@intel.com>
Date:   Mon, 16 Nov 2020 10:33:24 -0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <20201114084211.5284-1-hdanton@sina.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 11/14/20 12:42 AM, Hillf Danton wrote:
> On Fri, 13 Nov 2020 00:01:16 +0200 Jarkko Sakkinen wrote:
>> + */
>> +static void sgx_sanitize_section(struct sgx_epc_section *section)
>> +{
>> +	struct sgx_epc_page *page;
>> +	LIST_HEAD(dirty);
>> +	int ret;
>> +
>> +	while (!list_empty(&section->laundry_list)) {
>> +		if (kthread_should_stop())
>> +			return;
>> +
>> +		spin_lock(&section->lock);
>> +
>> +		page = list_first_entry(&section->laundry_list,
>> +					struct sgx_epc_page, list);
>> +
>> +		ret = __eremove(sgx_get_epc_virt_addr(page));
>> +		if (!ret)
>> +			list_move(&page->list, &section->page_list);
>> +		else
>> +			list_move_tail(&page->list, &dirty);
>> +
>> +		spin_unlock(&section->lock);
>> +
>> +		cond_resched();
>> +	}
>> +
>> +	list_splice(&dirty, &section->laundry_list);
> 
> Move list splice into the section under section->lock.

The naming, commenting and changelogs could be better here.  But, I
think the code is correct.

section->lock actually only protects ->page_list.

->laundry_list is initialized in core code, but after that is only used
by ksgxd and is effectively a thread-local structure.

I can think of a few other ways of doing this so that, for instance,
laundry_list was a thread-local structure in ksgxd that is freed after
initialization and sanitizing.  But, this is pretty simple, although
under-documented, and wastes a list_head worth of space per section at
runtime.

>> +}
> [...]
> 
>> +struct sgx_epc_page {
>> +	unsigned int section;
> 
> To make the sgx page naturally packed, add a small pad to match both
> sizeof(struct list_head) and X86_64. Feel free to turn back on the
> pad OTOH to save memory.

You make a good point: it's pretty obvious that the current code is
space-optimized.  That doesn't seem like a bad thing to me, though.