From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57E18C636CE for ; Tue, 20 Jul 2021 16:54:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3FC22610D2 for ; Tue, 20 Jul 2021 16:54:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230405AbhGTQNW (ORCPT ); Tue, 20 Jul 2021 12:13:22 -0400 Received: from mga12.intel.com ([192.55.52.136]:22084 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229638AbhGTQNJ (ORCPT ); Tue, 20 Jul 2021 12:13:09 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10051"; a="190861456" X-IronPort-AV: E=Sophos;i="5.84,255,1620716400"; d="scan'208";a="190861456" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jul 2021 09:53:16 -0700 X-IronPort-AV: E=Sophos;i="5.84,255,1620716400"; d="scan'208";a="469822709" Received: from kvadariv-mobl1.amr.corp.intel.com (HELO [10.212.155.118]) ([10.212.155.118]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jul 2021 09:53:15 -0700 Subject: Re: [PATCH v3 5/6] platform/x86: intel_tdx_attest: Add TDX Guest attestation interface driver To: Kuppuswamy Sathyanarayanan , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Peter Zijlstra , Andy Lutomirski , Hans de Goede , Mark Gross , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: Peter H Anvin , Tony Luck , Dan Williams , Andi Kleen , Kirill Shutemov , Sean Christopherson , Kuppuswamy Sathyanarayanan , x86@kernel.org, linux-kernel@vger.kernel.org, platform-driver-x86@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org References: <20210720045552.2124688-1-sathyanarayanan.kuppuswamy@linux.intel.com> <20210720045552.2124688-6-sathyanarayanan.kuppuswamy@linux.intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210720045552.2124688-6-sathyanarayanan.kuppuswamy@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > +/* Used in Quote memory allocation */ > +#define QUOTE_SIZE (2 * PAGE_SIZE) > +/* Get Quote timeout in msec */ > +#define GET_QUOTE_TIMEOUT (5000) The comment is good, but even better would be to call this: GET_QUOTE_TIMEOUT_MS > +/* Mutex to synchronize attestation requests */ > +static DEFINE_MUTEX(attestation_lock); > +/* Completion object to track attestation status */ > +static DECLARE_COMPLETION(attestation_done); > +/* Buffer used to copy report data in attestation handler */ > +static u8 report_data[TDX_REPORT_DATA_LEN]; > +/* Data pointer used to get TD Quote data in attestation handler */ > +static void *tdquote_data; > +/* Data pointer used to get TDREPORT data in attestation handler */ > +static void *tdreport_data; Are these *really* totally unknown, opaque blobs? Why not give them an actual data type? > +/* DMA handle used to allocate and free tdquote DMA buffer */ > +dma_addr_t tdquote_dma_handle; That's an unreadable jumble. Please add some line breaks and try to logically group those. > +static void attestation_callback_handler(void) > +{ > + complete(&attestation_done); > +} > + > +static long tdg_attest_ioctl(struct file *file, unsigned int cmd, > + unsigned long arg) > +{ > + void __user *argp = (void __user *)arg; > + long ret = 0; > + > + mutex_lock(&attestation_lock); > + > + switch (cmd) { > + case TDX_CMD_GET_TDREPORT: > + if (copy_from_user(report_data, argp, TDX_REPORT_DATA_LEN)) { > + ret = -EFAULT; > + break; > + } > + > + /* Generate TDREPORT_STRUCT */ > + if (tdx_mcall_tdreport(virt_to_phys(tdreport_data), > + virt_to_phys(report_data))) { Having that take a physical address seems like a mistake. Why not just do the virt_to_phys() inside the helper? Also, this isn't very clear that there is an input and an output. Can you rename these to make that more clear? > + ret = -EIO; > + break; > + } > + > + if (copy_to_user(argp, tdreport_data, TDX_TDREPORT_LEN)) > + ret = -EFAULT; > + break; > + case TDX_CMD_GEN_QUOTE: > + /* Copy TDREPORT data from user buffer */ > + if (copy_from_user(tdquote_data, argp, TDX_TDREPORT_LEN)) { > + ret = -EFAULT; > + break; > + } > + > + /* Submit GetQuote Request */ > + if (tdx_hcall_get_quote(virt_to_phys(tdquote_data))) { > + ret = -EIO; > + break; > + } > + > + /* Wait for attestation completion */ > + ret = wait_for_completion_interruptible_timeout( > + &attestation_done, > + msecs_to_jiffies(GET_QUOTE_TIMEOUT)); > + if (ret <= 0) { > + ret = -EIO; > + break; > + } > + > + if (copy_to_user(argp, tdquote_data, QUOTE_SIZE)) > + ret = -EFAULT; > + > + break; > + case TDX_CMD_GET_QUOTE_SIZE: > + ret = put_user(QUOTE_SIZE, (u64 __user *)argp); > + break; > + default: > + pr_err("cmd %d not supported\n", cmd); > + break; First of all, drivers shouldn't pollute the kernel log on bad input. Second, won't this inherit the ret=0 value and return success? > + } > + > + mutex_unlock(&attestation_lock); > + > + return ret; > +} > + > +static const struct file_operations tdg_attest_fops = { > + .owner = THIS_MODULE, > + .unlocked_ioctl = tdg_attest_ioctl, > + .llseek = no_llseek, > +}; > + > +static struct miscdevice tdg_attest_device = { > + .minor = MISC_DYNAMIC_MINOR, > + .name = "tdx-attest", > + .fops = &tdg_attest_fops, > +}; > + > +static int __init tdg_attest_init(void) > +{ > + dma_addr_t handle; > + long ret = 0; The function returns 'int', yet 'ret' is a long. Why? > + ret = misc_register(&tdg_attest_device); > + if (ret) { > + pr_err("misc device registration failed\n"); > + return ret; > + } > + > + tdreport_data = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 0); > + if (!tdreport_data) { > + ret = -ENOMEM; > + goto failed; > + } Why does this need to use the page allocator directly? Why does it need to zero the memory? Why does it need to get a whole page? If it really only needs a single page, why not use __get_free_page()? > + > + ret = dma_set_coherent_mask(tdg_attest_device.this_device, > + DMA_BIT_MASK(64)); > + if (ret) { > + pr_err("dma set coherent mask failed\n"); > + goto failed; > + } > + > + /* Allocate DMA buffer to get TDQUOTE data from the VMM */ > + tdquote_data = dma_alloc_coherent(tdg_attest_device.this_device, > + QUOTE_SIZE, &handle, > + GFP_KERNEL | __GFP_ZERO); > + if (!tdquote_data) { > + ret = -ENOMEM; > + goto failed; > + } > + > + tdquote_dma_handle = handle; > + > + /* > + * Currently tdg_event_notify_handler is only used in attestation > + * driver. But, WRITE_ONCE is used as benign data race notice. > + */ > + WRITE_ONCE(tdg_event_notify_handler, attestation_callback_handler); > + > + pr_debug("module initialization success\n"); > + > + return 0; > + > +failed: > + if (tdreport_data) > + free_pages((unsigned long)tdreport_data, 0); > + > + misc_deregister(&tdg_attest_device); > + > + pr_debug("module initialization failed\n"); > + > + return ret; > +} ...