From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.14]) (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 E03D81E47CC for ; Wed, 14 Jan 2026 00:24:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.14 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768350270; cv=none; b=P9PeOd74sPna4bjXQUUGzRcdgC+r1tnuOj61sjiSfaJhfc8ZJNWc+33+FKc8nuqmMKIN83rrK4S+fpD+Vq7py407luLRyyLi+aUDWMMlPdT91D9B3NHCHfasL7QXi09WWtLb8nzk1kLZAWQv4tvUP7buQLhFkvVPXovNt2PuzGQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768350270; c=relaxed/simple; bh=WqCsSyi76k4r56NtzdxY43LLmTK/iyv8s8ejjbX031A=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Hiw/dZqOs9EoO8Z7Z0SZgS7ZhEI7fLybsNkKCqRK0ntUkFZmAhyiKYMoRomS4259/TaHC0ZXn4RnI2kck8bcIIk2Y5u1TJhC3hZax6DqRV9F1Mikv4oxn+0YkF8s1gMRDRRA3VWf6Eig+bcqB51NXYdGtpHMSQXkryNwQunSGTM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Ou0GQvle; arc=none smtp.client-ip=192.198.163.14 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Ou0GQvle" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1768350269; x=1799886269; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=WqCsSyi76k4r56NtzdxY43LLmTK/iyv8s8ejjbX031A=; b=Ou0GQvlePWyGSmj/RhriTabk5sMuVKQr9Xclhl4ePOVxpvj9XRtq1tLp vLtSNGQKmiDpyIsqMAxTvrm9z5WsSGA8SQzD0K11CSWmfCtEmCxknNKMj pOS5So1YWa2u/ADN801xFEd5qpg7ADP597o9JSFm8ddcF2Hn8z98sFKt1 jOZdGqOa+TrlbpNwNyaMrbbWF0VhmkyPSmPn0U0hAKWkQcURt+iyDeiJp xadPIFBAGSHJERkxYTnF8pCV0ipFmEF5/JrnGr/cUN35NodlFnlJcHlT9 MA8o8AC+Sbx6IyC3X2wIGfTKlGGYB+Tor7f04skeelxN1ik/jwwqnhJYC A==; X-CSE-ConnectionGUID: 6MwvovAcSE+jf6JfI3qJAQ== X-CSE-MsgGUID: POmxoCy/QICYhDzxOHYSJw== X-IronPort-AV: E=McAfee;i="6800,10657,11670"; a="69698777" X-IronPort-AV: E=Sophos;i="6.21,224,1763452800"; d="scan'208";a="69698777" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by fmvoesa108.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jan 2026 16:24:28 -0800 X-CSE-ConnectionGUID: aOL48Z+KS92claLUcP6gwQ== X-CSE-MsgGUID: ZLJBOL7TT4u2x1tVeAPbRw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,224,1763452800"; d="scan'208";a="204942083" Received: from dnelso2-mobl.amr.corp.intel.com (HELO [10.125.110.189]) ([10.125.110.189]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jan 2026 16:24:27 -0800 Message-ID: <720020ac-b35c-4331-8434-457d170e4c68@intel.com> Date: Tue, 13 Jan 2026 17:24:26 -0700 Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/2] cxl/region: Translate HPA to DPA and memdev in unaligned regions To: Alison Schofield , Davidlohr Bueso , Jonathan Cameron , Vishal Verma , Ira Weiny , Dan Williams Cc: linux-cxl@vger.kernel.org References: <0d7d47672e81d0c4d9a4e5e335ca536dbecb9dee.1768008522.git.alison.schofield@intel.com> Content-Language: en-US From: Dave Jiang In-Reply-To: <0d7d47672e81d0c4d9a4e5e335ca536dbecb9dee.1768008522.git.alison.schofield@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/9/26 6:54 PM, Alison Schofield wrote: > The CXL driver supports an expert user debugfs interface to inject and > clear poison by a region offset. That feature requires translating a > HPA (the region address) to a DPA and a memdev to perform the poison > operation. > > Unaligned regions do not have an algebraically invertible mapping > from HPA to DPA due to the region offset skew. The region base is not > aligned to a full interleave. Add a helper to perform the unaligned > translations that first calculates the DPA offset and then tests it > against each candidate endpoint decoder. > > Signed-off-by: Alison Schofield Reviewed-by: Dave Jiang > --- > drivers/cxl/core/region.c | 46 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 46 insertions(+) > > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c > index 146ae9e42496..f63fc15ba0c1 100644 > --- a/drivers/cxl/core/region.c > +++ b/drivers/cxl/core/region.c > @@ -3307,6 +3307,48 @@ struct dpa_result { > u64 dpa; > }; > > +static int unaligned_region_offset_to_dpa_result(struct cxl_region *cxlr, > + u64 offset, > + struct dpa_result *result) > +{ > + struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent); > + struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld; > + struct cxl_region_params *p = &cxlr->params; > + u64 interleave_width, interleave_index; > + u64 gran, gran_offset, dpa_offset; > + u64 hpa = p->res->start + offset; > + > + /* > + * Unaligned addresses are not algebraically invertible. Calculate > + * a dpa_offset independent of the target device and then enumerate > + * and test that dpa_offset against each candidate endpoint decoder. > + */ > + gran = cxld->interleave_granularity; > + interleave_width = gran * cxld->interleave_ways; > + interleave_index = offset / interleave_width; > + gran_offset = offset % gran; > + > + dpa_offset = interleave_index * gran + gran_offset; > + > + for (int i = 0; i < p->nr_targets; i++) { > + struct cxl_endpoint_decoder *cxled = p->targets[i]; > + int pos = cxled->pos; > + u64 test_hpa; > + > + test_hpa = unaligned_dpa_to_hpa(cxld, p, pos, dpa_offset); > + if (test_hpa == hpa) { > + result->cxlmd = cxled_to_memdev(cxled); > + result->dpa = > + cxl_dpa_resource_start(cxled) + dpa_offset; > + return 0; > + } > + } > + dev_err(&cxlr->dev, > + "failed to resolve HPA %#llx in unaligned MOD3 region\n", hpa); > + > + return -ENXIO; > +} > + > static int region_offset_to_dpa_result(struct cxl_region *cxlr, u64 offset, > struct dpa_result *result) > { > @@ -3336,6 +3378,10 @@ static int region_offset_to_dpa_result(struct cxl_region *cxlr, u64 offset, > hpa_offset = offset; > } > > + if (region_is_unaligned_mod3(cxlr)) > + return unaligned_region_offset_to_dpa_result(cxlr, offset, > + result); > + > pos = cxl_calculate_position(hpa_offset, eiw, eig); > if (pos < 0 || pos >= p->nr_targets) { > dev_dbg(&cxlr->dev, "Invalid position %d for %d targets\n",