From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from BN1PR04CU002.outbound.protection.outlook.com (mail-eastus2azon11010060.outbound.protection.outlook.com [52.101.56.60]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B9B52302CD5; Fri, 20 Feb 2026 20:35:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.56.60 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771619759; cv=fail; b=m1eQU0EF6AMMno6ZPzF+qySQ3dHPP2EkyApILxAK+9K4Q8acHfiKCfhopWX/49nMW5EV+tScCxgjeopoB4SiV4H/vMy5jGinyySe2Cv4Ik8BCNDgEFvjxQjyVuNuo0kH6B5hs82WPAwexncvx0G796AM8pBZJoA1WxUfnmNuPiE= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771619759; c=relaxed/simple; bh=gGu8yobnmahZ/kvroWuHPIA8jKjwYmApOkYX34eAD2w=; h=Message-ID:Date:Subject:To:Cc:References:From:In-Reply-To: Content-Type:MIME-Version; b=MwHPvH8cqgLk1Zvrm1OsxgEDgHpP/xOTtda9pW7AWAuzvZgEiHtKJ5TfdAakxPK6FeEVjjubLvHP+INTDS80Dh1aM9Ym78o8Ak6ToQrPUuhFRupSChmjckQjXZNQRAT+IhMVGlycJrEsipg7wKchJb1F4JJQTnEh9sPziHBbmVg= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com; spf=fail smtp.mailfrom=amd.com; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b=sSzWbuxm; arc=fail smtp.client-ip=52.101.56.60 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=amd.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b="sSzWbuxm" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=FT5LmOj+TEl2ggB8PI2a9VgFrGIQ5NFPMpuyBSl4+LywxGS7XeMbljLWsoXXeMz5o3oSzwRu/ZplAtdHUI/cTYuLUBEhJZGOpFkZ8Ov2Ryu9kpKEEiZTjTZTfJ+WHkEJS1Dfa6c3JEp+YpQz93GlQxCMVKTYjTVFpKvRrJdjZEyFgAyeHsVVVrtKQUkzemuC0KyME0LgYhQw88554B4OifhS6VEOW71cv+5ArngTfJprPtfbrTXb+WYd2YsSbZ078DH+rog0UCWx+7jJM4xzkzrzKgtsaeYQOP5AofdyR84NhyKc9GkC0+7DCuOw8OfSuUATO/BxZd2S0KRyvIfR7w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=NqTxJETkMcn67sKuuF29Q3akie+wpFXKEKGdqWrBHcM=; b=a5RYZcyXTKfCNpBil4VJHVEVj6Wpf5KdWmOF7s8a2YH/GJjR/i3kRetIpJ2DW0dlJEPGhXaYbsra6hK7WbrTYM8dqCaczjk9BQrt67cL0JCRg+Pk5/SVAJWlm02S9+zzHR3qKBF1cnvtVctm4y8YObo8CgCZZo11q6YvtaSjKVpnB7DhE26lLnnWXvd5eAcTSePJWew3dMAVFq4XWTJ2IA7ecmxpXf7MJF649C8dHz3lfT4Hi2d8jwuiOdfh5tglLkV+m9FTO0xvu7tfSfidjaEqfx2fZho9oei/S2fUkYmye42dDA1RSCTGhysoR19505GPfSeI7bJqXpsCVaI2Fw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=amd.com; dmarc=pass action=none header.from=amd.com; dkim=pass header.d=amd.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=NqTxJETkMcn67sKuuF29Q3akie+wpFXKEKGdqWrBHcM=; b=sSzWbuxm1w2AYZQfeSHGR7A/NKV5LzL9YiLr5StbagmDKt9MLg0m7f4g8996nVb1TkL0if3Sq8+k26dsng+F8mJcIfbVoqS/5UcBtsyx1H8pL78iqAcI4LoXSw3UoBmHyWJqO2GvrexfMuhDam7p0INyRPfC/VRvyyeamtGeOgM= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from LV8PR12MB9714.namprd12.prod.outlook.com (2603:10b6:408:2a0::5) by PH7PR12MB7212.namprd12.prod.outlook.com (2603:10b6:510:207::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9632.16; Fri, 20 Feb 2026 20:35:51 +0000 Received: from LV8PR12MB9714.namprd12.prod.outlook.com ([fe80::8c9f:3a5b:974b:99c6]) by LV8PR12MB9714.namprd12.prod.outlook.com ([fe80::8c9f:3a5b:974b:99c6%6]) with mapi id 15.20.9632.015; Fri, 20 Feb 2026 20:35:49 +0000 Message-ID: <909004d4-f1d5-4fe7-a71f-11d9c6885cac@amd.com> Date: Fri, 20 Feb 2026 12:35:45 -0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 3/9] cxl/region: Skip decoder reset on detach for autodiscovered regions To: Alison Schofield , Smita Koralahalli Cc: linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-pm@vger.kernel.org, Ard Biesheuvel , Vishal Verma , Ira Weiny , Dan Williams , Jonathan Cameron , Yazen Ghannam , Dave Jiang , Davidlohr Bueso , Matthew Wilcox , Jan Kara , "Rafael J . Wysocki" , Len Brown , Pavel Machek , Li Ming , Jeff Johnson , Ying Huang , Yao Xingtao , Peter Zijlstra , Greg Kroah-Hartman , Nathan Fontenot , Terry Bowman , Robert Richter , Benjamin Cheatham , Zhijian Li , Borislav Petkov , Tomasz Wolski References: <20260210064501.157591-1-Smita.KoralahalliChannabasappa@amd.com> <20260210064501.157591-4-Smita.KoralahalliChannabasappa@amd.com> Content-Language: en-US From: "Koralahalli Channabasappa, Smita" In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR05CA0023.namprd05.prod.outlook.com (2603:10b6:a03:c0::36) To LV8PR12MB9714.namprd12.prod.outlook.com (2603:10b6:408:2a0::5) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV8PR12MB9714:EE_|PH7PR12MB7212:EE_ X-MS-Office365-Filtering-Correlation-Id: ecad083e-c25a-4d61-3ced-08de70bfa1d4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|366016|1800799024; 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For > > Not sure 'detached' is the right word. Unregistered maybe? > >> autodiscovered regions, this can incorrectly tear down decoder state >> that may be relied upon by other consumers or by subsequent ownership >> decisions. >> >> Skip cxl_region_decode_reset() during detach when CXL_REGION_F_AUTO is >> set. > > I get how this is needed in the failover to DAX case, yet I'm not clear > how it fits in with folks that just want to destroy that auto region > and resuse the pieces. > > Your other recent patch cxl/hdm: Avoid DVSEC fallback after region teardown[1], > showed me that the memdevs, when left with the endpoint decoders not reset, > will keep trying to create another region when reprobed. > > [1] https://lore.kernel.org/linux-cxl/aY6pTk63ivjkanlR@aschofie-mobl2.lan/ > > I think the patch does what it says it does. Perhaps expand on why that > is always the right thing to do. > > --Alison > > >> Thanks for the review. I will fix detached to unregistered in the commit message for v7. I think there are two paths here: Correct me if I'm wrong. F_AUTO guard only applies to __cxl_decoder_detach(), which is called from unregister_region() (unregister_region()->detach_target()->cxl_decoder_detach()..) path and via store_targetN() (store_targetN()->detach_target()->cxl_decoder_detach()..). In both cases, this patch is preserving decoder state for auto-discovered regions. When a user explicitly destroys an auto-discovered region via cxl destroy-region, or decommits via commit_store, those paths call cxl_region_decode_reset() (commit_store()->cxl_region_decode_reset()->cxld->reset) unconditionally, they are not gated by F_AUTO. So users who want to destroy the auto region and reuse the pieces can still do so. The decoder state is fully reset in that path. On the DVSEC fallback fix: The endpoint decoders were being reset (by cxl_region_decode_reset() unconditionally), which zeroed the registers. On reprobe, should_emulate_decoders() checked per decoder COMMITTED bits, found them cleared, and incorrectly fell back to DVSEC range emulation, treating the decoder as AUTO and creating a spurious region.. Also, since nothing in the dax_hmem path calls unregister_region today, this F_AUTO guard in __cxl_decoder_detach() is only for preserving firmware decoder state during auto region teardown. I need to rephrase that in commit message properly. I will also expand the commit message for v7 documenting how the explicit decommit path still remains available. Thanks Smita >> Signed-off-by: Smita Koralahalli >> Reviewed-by: Jonathan Cameron >> Reviewed-by: Dave Jiang >> Reviewed-by: Alejandro Lucero >> --- >> drivers/cxl/core/region.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c >> index ae899f68551f..45ee598daf95 100644 >> --- a/drivers/cxl/core/region.c >> +++ b/drivers/cxl/core/region.c >> @@ -2178,7 +2178,9 @@ __cxl_decoder_detach(struct cxl_region *cxlr, >> cxled->part = -1; >> >> if (p->state > CXL_CONFIG_ACTIVE) { >> - cxl_region_decode_reset(cxlr, p->interleave_ways); >> + if (!test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) >> + cxl_region_decode_reset(cxlr, p->interleave_ways); >> + >> p->state = CXL_CONFIG_ACTIVE; >> } >> >> -- >> 2.17.1 >>