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07 Nov 2018 09:41:06 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,476,1534834800"; d="scan'208";a="106710316" Received: from schen9-desk.jf.intel.com (HELO [10.54.74.144]) ([10.54.74.144]) by orsmga002.jf.intel.com with ESMTP; 07 Nov 2018 09:41:06 -0800 To: Aubrey Li , tglx@linutronix.de, mingo@redhat.com, peterz@infradead.org, hpa@zytor.com Cc: ak@linux.intel.com, arjan@linux.intel.com, linux-kernel@vger.kernel.org, Aubrey Li References: <1541528590-30296-1-git-send-email-aubrey.li@intel.com> From: Tim Chen Openpgp: preference=signencrypt Autocrypt: addr=tim.c.chen@linux.intel.com; prefer-encrypt=mutual; keydata= xsFNBE6ONugBEAC1c8laQ2QrezbYFetwrzD0v8rOqanj5X1jkySQr3hm/rqVcDJudcfdSMv0 BNCCjt2dofFxVfRL0G8eQR4qoSgzDGDzoFva3NjTJ/34TlK9MMouLY7X5x3sXdZtrV4zhKGv 3Rt2osfARdH3QDoTUHujhQxlcPk7cwjTXe4o3aHIFbcIBUmxhqPaz3AMfdCqbhd7uWe9MAZX 7M9vk6PboyO4PgZRAs5lWRoD4ZfROtSViX49KEkO7BDClacVsODITpiaWtZVDxkYUX/D9OxG AkxmqrCxZxxZHDQos1SnS08aKD0QITm/LWQtwx1y0P4GGMXRlIAQE4rK69BDvzSaLB45ppOw AO7kw8aR3eu/sW8p016dx34bUFFTwbILJFvazpvRImdjmZGcTcvRd8QgmhNV5INyGwtfA8sn L4V13aZNZA9eWd+iuB8qZfoFiyAeHNWzLX/Moi8hB7LxFuEGnvbxYByRS83jsxjH2Bd49bTi XOsAY/YyGj6gl8KkjSbKOkj0IRy28nLisFdGBvgeQrvaLaA06VexptmrLjp1Qtyesw6zIJeP oHUImJltjPjFvyfkuIPfVIB87kukpB78bhSRA5mC365LsLRl+nrX7SauEo8b7MX0qbW9pg0f wsiyCCK0ioTTm4IWL2wiDB7PeiJSsViBORNKoxA093B42BWFJQARAQABzTRUaW0gQ2hlbiAo d29yayByZWxhdGVkKSA8dGltLmMuY2hlbkBsaW51eC5pbnRlbC5jb20+wsF+BBMBAgAoAhsD BgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAUCWfPBPgUJDyfxUQAKCRCiZ7WKota4SReFEACa 5ruzJM/hXJguHJY8i95rxHfLOgE7QoDgsR2aK2C1BSu84StTcT9BMikndQ0em28mpd1zROCs FvJ8Dzpp923699FU7s70+bFG9zIWtAOLWt2QyIMYImILzKkzkyLZo2RTcLNdUWS5fkAtjspQ QPg29W+kcbX1NhB6WDdbvk2HNeZoDh4A5ucOzKjEPqbSFIbw2Wt3RUmXxezjH1NzZG3fMkEN cT7JezYhUxvi2PrJlD+mo26q2/PQmFgF49tneRJXmYyie5o2+ClfFVO9I6Rd1k7hS9uXQLg3 udpnDKobNYZ7/+O5+ucp0Y/MwzTfBYmtJ5fBjUTi2L1RMDJee8WqCNY1VU6cQ8MD4KstxUp2 bxlSRAYaDtNa1Omr61E7BA1Cc2E3cIt/O1mMfudWUjCND8qrAtEnugqKjk5tJJZzmzIKSHPY dCiJtOBQaVAYYchXF2hwOKhpFS43V4FdWLlM1CnFXsmbk48hGbiA8XHU85JBCXmG0i4qUlKn x2ilChvq4A102ahnlGbEmFaSwxuqR/5lhai6lOkwHXDFUT6jblaSs24L3MTn/vXtvwaLEEKh SPzNaj7yFvEhrJoLiZmDm0SZuPbQ+wrmPWUbzyf5te2Oq0JyrHTQJoQqn+CwGqwF/JaUq60f VuUD3T0icgsfljsOA4apyH7kyfxXGP0hOM7BTQROjjboARAAx+LxKhznLH0RFvuBEGTcntrC 3S0tpYmVsuWbdWr2ZL9VqZmXh6UWb0K7w7OpPNW1FiaWtVLnG1nuMmBJhE5jpYsi+yU8sbMA 5BEiQn2hUo0k5eww5/oiyNI9H7vql9h628JhYd9T1CcDMghTNOKfCPNGzQ8Js33cFnszqL4I N9jh+qdg5FnMHs/+oBNtlvNjD1dQdM6gm8WLhFttXNPn7nRUPuLQxTqbuoPgoTmxUxR3/M5A KDjntKEdYZziBYfQJkvfLJdnRZnuHvXhO2EU1/7bAhdz7nULZktw9j1Sp9zRYfKRnQdIvXXa jHkOn3N41n0zjoKV1J1KpAH3UcVfOmnTj+u6iVMW5dkxLo07CddJDaayXtCBSmmd90OG0Odx cq9VaIu/DOQJ8OZU3JORiuuq40jlFsF1fy7nZSvQFsJlSmHkb+cDMZDc1yk0ko65girmNjMF hsAdVYfVsqS1TJrnengBgbPgesYO5eY0Tm3+0pa07EkONsxnzyWJDn4fh/eA6IEUo2JrOrex O6cRBNv9dwrUfJbMgzFeKdoyq/Zwe9QmdStkFpoh9036iWsj6Nt58NhXP8WDHOfBg9o86z9O VMZMC2Q0r6pGm7L0yHmPiixrxWdW0dGKvTHu/DH/ORUrjBYYeMsCc4jWoUt4Xq49LX98KDGN dhkZDGwKnAUAEQEAAcLBZQQYAQIADwIbDAUCVEAL2AUJC1VvawAKCRCiZ7WKota4SWWrD/9L 4H3kHUR9qPTfSpwFBV0+PspkpMQmRQ9cQauIRXL+qIqCYfx48Jz/WZkq47COhY4d1tAvX4qv lviIoCwShAHhVkxD2rWFpa6Yang7cyPDjS6sNChsZ9aTAP0zX4LLHN8ub5LwCcU9JA4Avwdy NDSeeSeqNq9QOvVd2bDmyHxgVv4zRgLTNPH28hXAnDODy0wCJWg53PWvlp35XfWdIsC0ZAPK vgA1Bh+FYYKfT8Uzj8J/SYH+chmeYMt+8Y+FZa+NybivWJg6+UaJ2fCTuKCc7TgqLneBudox izWQMnBso0tHOT6+ju+L+ewPWc0OrJdKJeadrE2T1E949vMup5jG0lJLeSpBNmELODNL0xz6 Erjs/pwX7cYGKUbJfBaQcC9frPfpWfSqnK5X+12HFDxAxquXKC4ejBJOhbo3xx0sziiPTC3m 4LvLkEa9evQNtMvRcnWY5qIC4YdT5waC0stYNpyCiBXpYArKYCmlra3xpgAe0MRL94PHU4UW yxxdxRubFYna9LeNcWL7C0w2ngg1jd0tjRjLnimrOL8rSVUzwjNSQOV37tWTueTr40M/SfjU B6bifflZQpeSY8IpqzKqB0vvxo2xD0rU7JqUh7rW8U6rg2JEzVgYiHS4cf/vJMHuauHAjH7a ys7DYlLhlOVo3o0jOor4xuZPrWbSp4w51sLBZQQYAQIADwIbDAUCWfPBJQUJDyfxOAAKCRCi Z7WKota4SZKQD/wLu3j8kgATic+wF3ekngjwPcW3JhbQJeHxUZwsb9OgVMHumlrZHGoltKQu FfAhG/sOfuAh5f7QMzzA1M+2JD1Q6lr74vUHNBu+xBFMgZstE6hpkKmn0pNZ5JS3iZRVRLBx dWw63DYr0GM80vmbHjAhwxoF2PsO2/PkWTc68+pFyl3Dy0heZSJii81hkzh8FnF8CaMH0VXu MJoWyuYgnC058hHj0QqXvlNx9LzMtmrsskTmPvwqXTgG/dTEfTkQ4RfX3enrBy55cg9tMc88 BEQ/0/JV1bCDwyWXKRpz6FsHbICGQ4G9TTD4pS5QJ+oRQccMjfiDM3rFTcG1RYP2lHXjSm9c 0VnimpQBz3LarrdHJilmTHbAWf5KLmtWfYXHrlncnhnCtw2nfwBBdy8cQW4tUyniSVRLOwGm eJziyuPJ5SVVZcil2oN5/o7js7BYAeAV/WVF2Sk/blnXaaObIYIVqnDhV4N0oUz1KXq1Leem Uvjo5rljmmhOBdgl6D0scXCWICbuuWN9eW2fZl38hBSI3M0MX0jnV2e+0FY+76iNmKadpTDw gY3OaQAZ/UlJVI+pRV4JtRrajtpo9Vb38SBPXwp9moWmwVQyIdFUXjCTQARvxjRsUoPVu9oA SCd9W74oOgrqC1hadvVU867d07PlWksfYwCeYP4bs+4GSLzI1w== Subject: Re: [RFC PATCH v1 1/2] x86/fpu: detect AVX task Message-ID: Date: Wed, 7 Nov 2018 09:41:05 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 MIME-Version: 1.0 In-Reply-To: <1541528590-30296-1-git-send-email-aubrey.li@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/06/2018 10:23 AM, Aubrey Li wrote: > +static inline void update_avx_state(struct avx_state *avx) > +{ > + /* > + * Check if XGETBV with ECX = 1 supported. XGETBV with ECX = 1 > + * returns the logical-AND of XCR0 and XINUSE. XINUSE is a bitmap > + * by which the processor tracks the status of various components. > + */ > + if (!use_xgetbv1()) { > + avx->state = 0; > + return; > + } > + /* > + * XINUSE is dynamic to track component state because VZEROUPPER > + * happens on every function end and reset the bitmap to the > + * initial configuration. > + * > + * State decay is introduced to solve the race condition between > + * context switch and a function end. State is aggressively set > + * once it's detected but need to be cleared by decay 3 context > + * switches > + */ > + if (xgetbv(XINUSE_STATE_BITMAP_INDEX) & XFEATURE_MASK_Hi16_ZMM) { > + avx->state = 1; > + avx->decay_count = AVX_STATE_DECAY_COUNT; > + } else { > + if (!avx->decay_count) Seems like the check should be if (avx->decay_count) as we decrement the decay_count if it is non-zero. > + avx->decay_count--; > + else > + avx->state = 0; > + } > +} Tim