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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A7EF9ECAAD8 for ; Wed, 21 Sep 2022 14:15:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229885AbiIUOPW (ORCPT ); Wed, 21 Sep 2022 10:15:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49572 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229498AbiIUOPU (ORCPT ); Wed, 21 Sep 2022 10:15:20 -0400 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E5BA50184; Wed, 21 Sep 2022 07:15:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1663769719; x=1695305719; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=kV8SvwzQDpNaPqI8Ad9CXg1aOsjOIFy6gAewf2bsPso=; b=C+IDKMZZZu1HqM28naUEdwm6iKYjg6M2I0BFK/eueceo80ajSuQmGnDD 6JvD5p5edjGfCCZZf+hjWYx42OZrAPurzAlvSMxe1xNU7fHG9C1KgVre0 oXpXuqMh74At8GSbRa6VHGAluRQfYfLgo2Ads+vmVN5Ci5Yu89yeNhBHi QVzVzcYMmvSkp0CdFMW6rl1XIDsD1Ex01gycpFYBkbbURqfgw3IlRelqD NsL4WwHcEaoUrfTzZx7WjamUCjo3pxrVBXPWaL2QnNhv1OEQlmb/7Xh5W 6lP7phEA8sOEJxuI3Q/dAnJor2TAVQWU0IV03WWo71CfnlpD+K43EHpNn Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10477"; a="299999188" X-IronPort-AV: E=Sophos;i="5.93,333,1654585200"; d="scan'208";a="299999188" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2022 07:15:08 -0700 X-IronPort-AV: E=Sophos;i="5.93,333,1654585200"; d="scan'208";a="687890947" Received: from ryero-mobl.amr.corp.intel.com (HELO [10.209.89.231]) ([10.209.89.231]) by fmsmga004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2022 07:15:07 -0700 Message-ID: <2b6143b6-9db4-05bc-1e8d-c5d129126f99@intel.com> Date: Wed, 21 Sep 2022 07:15:07 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH] ACPI: processor_idle: Skip dummy wait for processors based on the Zen microarchitecture Content-Language: en-US To: K Prateek Nayak , linux-kernel@vger.kernel.org Cc: rafael@kernel.org, lenb@kernel.org, linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, dave.hansen@linux.intel.com, bp@alien8.de, tglx@linutronix.de, andi@lisas.de, puwen@hygon.cn, mario.limonciello@amd.com, peterz@infradead.org, rui.zhang@intel.com, gpiccoli@igalia.com, daniel.lezcano@linaro.org, ananth.narayan@amd.com, gautham.shenoy@amd.com, Calvin Ong , stable@vger.kernel.org, regressions@lists.linux.dev References: <20220921063638.2489-1-kprateek.nayak@amd.com> From: Dave Hansen In-Reply-To: <20220921063638.2489-1-kprateek.nayak@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 9/20/22 23:36, K Prateek Nayak wrote: > + /* > + * No delay is needed if we are in guest or on a processor > + * based on the Zen microarchitecture. > + */ > + if (boot_cpu_has(X86_FEATURE_HYPERVISOR) || boot_cpu_has(X86_FEATURE_ZEN)) > return; In the end, the delay is because of buggy, circa 2006 chipsets? So, we use a CPU vendor specific check to approximate that the chipset is recent and not affected by the bug? If so, is there no better way to check for a newer chipset than this? Do X86_FEATURE_ZEN CPUs just have unusually painful inl(acpi_fadt.xpm_tmr_blk.address) implementations? Is that why we noticed all of a sudden?