From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.9]) (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 DF99A72622; Thu, 28 May 2026 00:16:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779927409; cv=none; b=N82UD5dbbJRzDOUybgloK9C9GU+Qs7YN0tP2/MDUXrsA03E8mnjfhHJjKTXzavjnnjHKbks05vyUmQcHLB/4eJ3FDso62o2VYGNHRF+QWcgw1MD0180klVtX87hyq+O5Cj9vbMmL5Rj7JM/yGrXv9uJv0JZjOxqAyhheePc2Hq4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779927409; c=relaxed/simple; bh=J+LjVxnzSxVul7xVtHw+36L152ElbxAsNv2/mNnuLSw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rehjfPhqmNdRhXFa0fHKd9i84jPwZeq1HZaNN1gdD9MmqV4pc9845bceBj72ez4/Jko2uFi37t1rPuUDI6t7tnw1vfgNiSanwKXHvRgh7JMbSTvJ5WvMba+tY8EfPUy/oqQvF8t43ygW8PH+j42NCuRITr245ggeSXKVb7VGYfk= 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=VNOiaPGz; arc=none smtp.client-ip=192.198.163.9 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="VNOiaPGz" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1779927407; x=1811463407; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=J+LjVxnzSxVul7xVtHw+36L152ElbxAsNv2/mNnuLSw=; b=VNOiaPGzKOjoXoJJCJ9divAxrwWMmryc3Y3FFAHv4TaS5s9Jm/J8cFgF UHVrigh93TpbHM3Nv6qv2xbKr/y6YeO6QLEU7Mkpkr5RsNxy6ggxc7U8b UW4GcwBU2vUKqf+LiPknSmvHhKrpi6zzOMmT7lZBs6aChfK45V4/s1/n8 gD4iTsgMglxLF0pzTiMuYM61RdSY8Euk70RbiL9sEY+Pd3PouYQXrXfKd QPc3y5siw/xnlrbpRSoLUu+/IJkAuWObOC5QSWOGZ9COHLaoy404ACF0P cr4tWpyBKwVKSYGhtUnN9SUaYMWc4P5xznEs0KVCXF3MfNqxG7aBChoTk Q==; X-CSE-ConnectionGUID: fQyxf5eBTImRcwS+6/Nfxg== X-CSE-MsgGUID: zDsNAhQnSq2SwdvuTxwXJA== X-IronPort-AV: E=McAfee;i="6800,10657,11799"; a="91457140" X-IronPort-AV: E=Sophos;i="6.24,172,1774335600"; d="scan'208";a="91457140" Received: from orviesa006.jf.intel.com ([10.64.159.146]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 May 2026 17:16:46 -0700 X-CSE-ConnectionGUID: mDWPMm8VSuK4v0lZvkpfJA== X-CSE-MsgGUID: sKm5IM6dQbyH0IFD7V/LOg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.24,172,1774335600"; d="scan'208";a="241359486" Received: from rfrazer-mobl3.amr.corp.intel.com (HELO [10.125.111.23]) ([10.125.111.23]) by orviesa006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 May 2026 17:16:45 -0700 Message-ID: Date: Wed, 27 May 2026 17:16:44 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 07/31] cxl/region: Add DC DAX region support To: Anisa Su , linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org Cc: nvdimm@lists.linux.dev, Dan Williams , Jonathan Cameron , Davidlohr Bueso , Vishal Verma , Ira Weiny , Alison Schofield , John Groves , Gregory Price , Ira Weiny References: <9f0e0b3deeb1825ad113d7aebe7056dcf2bbc5f9.1779528761.git.anisa.su@samsung.com> Content-Language: en-US From: Dave Jiang In-Reply-To: <9f0e0b3deeb1825ad113d7aebe7056dcf2bbc5f9.1779528761.git.anisa.su@samsung.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/23/26 2:43 AM, Anisa Su wrote: > From: Ira Weiny > > DC DAX regions must allow memory to be added or removed dynamically. > In addition to the quantity of memory available the, > location of the memory within a DC partition is dynamic, based on the > extents offered by a device. CXL DAX regions must accommodate the > dynamic movement of this memory in the management of DAX regions and devices. > > Introduce the concept of a dynamic DAX region. Introduce > create_dynamic_ram_a_region() sysfs entry to create such regions. > Special case DC-capable regions to create a 0 sized seed DAX device > to maintain compatibility which requires a default DAX device to hold a > region reference. > > Indicate 0 byte available capacity until such time that capacity is > added. > > Dynamic regions complicate the range mapping of dax devices. There is no > known use case for range mapping on dynamic regions. Avoid the > complication by preventing range mapping of dax devices on dynamic > regions. > > Interleaving is deferred for now. Add checks. > > Based on an original patch by Navneet Singh. > > Signed-off-by: Ira Weiny Missing Anisa sign off > > --- > Changes: > [anisa: rebase] > [anisa: change "sparse" naming conventions and to "dynamic"] > --- > Documentation/ABI/testing/sysfs-bus-cxl | 22 ++++++++--------- > drivers/cxl/core/core.h | 11 +++++++++ > drivers/cxl/core/port.c | 1 + > drivers/cxl/core/region.c | 33 +++++++++++++++++++++++-- > drivers/cxl/core/region_dax.c | 6 +++++ > drivers/dax/bus.c | 10 ++++++++ > drivers/dax/bus.h | 1 + > drivers/dax/cxl.c | 17 +++++++++++-- > 8 files changed, 86 insertions(+), 15 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl > index c604c7ca6432..3080aef9ad67 100644 > --- a/Documentation/ABI/testing/sysfs-bus-cxl > +++ b/Documentation/ABI/testing/sysfs-bus-cxl > @@ -434,20 +434,20 @@ Description: > interleave_granularity). > > > -What: /sys/bus/cxl/devices/decoderX.Y/create_{pmem,ram}_region > -Date: May, 2022, January, 2023 > -KernelVersion: v6.0 (pmem), v6.3 (ram) > +What: /sys/bus/cxl/devices/decoderX.Y/create_{pmem,ram,dynamic_ram_a}_region > +Date: May, 2022, January, 2023, May 2025 > +KernelVersion: v6.0 (pmem), v6.3 (ram), v6.16 (dynamic_ram_a) update > Contact: linux-cxl@vger.kernel.org > Description: > (RW) Write a string in the form 'regionZ' to start the process > - of defining a new persistent, or volatile memory region > - (interleave-set) within the decode range bounded by root decoder > - 'decoderX.Y'. The value written must match the current value > - returned from reading this attribute. An atomic compare exchange > - operation is done on write to assign the requested id to a > - region and allocate the region-id for the next creation attempt. > - EBUSY is returned if the region name written does not match the > - current cached value. > + of defining a new persistent, volatile, or dynamic RAM memory > + region (interleave-set) within the decode range bounded by root > + decoder 'decoderX.Y'. The value written must match the current > + value returned from reading this attribute. An atomic compare > + exchange operation is done on write to assign the requested id > + to a region and allocate the region-id for the next creation > + attempt. EBUSY is returned if the region name written does not > + match the current cached value. > > > What: /sys/bus/cxl/devices/decoderX.Y/delete_region > diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h > index 82ca3a476708..8881cc9323e0 100644 > --- a/drivers/cxl/core/core.h > +++ b/drivers/cxl/core/core.h > @@ -6,6 +6,7 @@ > > #include > #include > +#include > > extern const struct device_type cxl_nvdimm_bridge_type; > extern const struct device_type cxl_nvdimm_type; > @@ -18,6 +19,15 @@ enum cxl_detach_mode { > DETACH_INVALIDATE, > }; > > +static inline struct cxl_memdev_state * > +cxled_to_mds(struct cxl_endpoint_decoder *cxled) > +{ > + struct cxl_memdev *cxlmd = cxled_to_memdev(cxled); > + struct cxl_dev_state *cxlds = cxlmd->cxlds; > + > + return container_of(cxlds, struct cxl_memdev_state, cxlds); return to_cxl_memdev_state(cxlmd->cxlds); > +} > + > #ifdef CONFIG_CXL_REGION > > struct cxl_region_context { > @@ -29,6 +39,7 @@ struct cxl_region_context { > > extern struct device_attribute dev_attr_create_pmem_region; > extern struct device_attribute dev_attr_create_ram_region; > +extern struct device_attribute dev_attr_create_dynamic_ram_a_region; > extern struct device_attribute dev_attr_delete_region; > extern struct device_attribute dev_attr_region; > extern const struct device_type cxl_pmem_region_type; > diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c > index a7f71f36531f..2d33001dac26 100644 > --- a/drivers/cxl/core/port.c > +++ b/drivers/cxl/core/port.c > @@ -337,6 +337,7 @@ static struct attribute *cxl_decoder_root_attrs[] = { > &dev_attr_qos_class.attr, > SET_CXL_REGION_ATTR(create_pmem_region) > SET_CXL_REGION_ATTR(create_ram_region) > + SET_CXL_REGION_ATTR(create_dynamic_ram_a_region) With this add, may need to add checks in cxl_root_decoder_visible() for dynamic_ram for create and also delete. > SET_CXL_REGION_ATTR(delete_region) > NULL, > }; > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c > index edc267c6cf77..7561bf3d8af8 100644 > --- a/drivers/cxl/core/region.c > +++ b/drivers/cxl/core/region.c > @@ -493,6 +493,11 @@ static int set_interleave_ways(struct cxl_region *cxlr, int val) > int save, rc; > u8 iw; > > + if (cxlr->mode == CXL_PARTMODE_DYNAMIC_RAM_A && val != 1) { > + dev_err(&cxlr->dev, "Interleaving and DCD not supported\n"); > + return -EINVAL; > + } > + > rc = ways_to_eiw(val, &iw); > if (rc) > return rc; > @@ -2389,6 +2394,7 @@ static size_t store_targetN(struct cxl_region *cxlr, const char *buf, int pos, > if (sysfs_streq(buf, "\n")) > rc = detach_target(cxlr, pos); > else { > + struct cxl_endpoint_decoder *cxled; > struct device *dev; > > dev = bus_find_device_by_name(&cxl_bus_type, NULL, buf); > @@ -2400,8 +2406,14 @@ static size_t store_targetN(struct cxl_region *cxlr, const char *buf, int pos, > goto out; > } > > - rc = attach_target(cxlr, to_cxl_endpoint_decoder(dev), pos, > - TASK_INTERRUPTIBLE); > + cxled = to_cxl_endpoint_decoder(dev); > + if (cxlr->mode == CXL_PARTMODE_DYNAMIC_RAM_A && > + !cxl_dcd_supported(cxled_to_mds(cxled))) { cxled_to_mds() can return NULL with the earlier change suggested. Need to handle that DJ > + dev_dbg(dev, "DCD unsupported\n"); > + rc = -EINVAL; > + goto out; > + } > + rc = attach_target(cxlr, cxled, pos, TASK_INTERRUPTIBLE); > out: > put_device(dev); > } > @@ -2750,6 +2762,7 @@ static struct cxl_region *__create_region(struct cxl_root_decoder *cxlrd, > switch (mode) { > case CXL_PARTMODE_RAM: > case CXL_PARTMODE_PMEM: > + case CXL_PARTMODE_DYNAMIC_RAM_A: > break; > default: > dev_err(&cxlrd->cxlsd.cxld.dev, "unsupported mode %d\n", mode); > @@ -2802,6 +2815,21 @@ static ssize_t create_ram_region_store(struct device *dev, > } > DEVICE_ATTR_RW(create_ram_region); > > +static ssize_t create_dynamic_ram_a_region_show(struct device *dev, > + struct device_attribute *attr, > + char *buf) > +{ > + return __create_region_show(to_cxl_root_decoder(dev), buf); > +} > + > +static ssize_t create_dynamic_ram_a_region_store(struct device *dev, > + struct device_attribute *attr, > + const char *buf, size_t len) > +{ > + return create_region_store(dev, buf, len, CXL_PARTMODE_DYNAMIC_RAM_A); > +} > +DEVICE_ATTR_RW(create_dynamic_ram_a_region); > + > static ssize_t region_show(struct device *dev, struct device_attribute *attr, > char *buf) > { > @@ -4081,6 +4109,7 @@ static int cxl_region_probe(struct device *dev) > > return devm_cxl_add_pmem_region(cxlr); > case CXL_PARTMODE_RAM: > + case CXL_PARTMODE_DYNAMIC_RAM_A: > rc = devm_cxl_region_edac_register(cxlr); > if (rc) > dev_dbg(&cxlr->dev, "CXL EDAC registration for region_id=%d failed\n", > diff --git a/drivers/cxl/core/region_dax.c b/drivers/cxl/core/region_dax.c > index de04f78f6ad8..d6bf69155827 100644 > --- a/drivers/cxl/core/region_dax.c > +++ b/drivers/cxl/core/region_dax.c > @@ -84,6 +84,12 @@ int devm_cxl_add_dax_region(struct cxl_region *cxlr) > struct device *dev; > int rc; > > + if (cxlr->mode == CXL_PARTMODE_DYNAMIC_RAM_A && > + cxlr->params.interleave_ways != 1) { > + dev_err(&cxlr->dev, "Interleaving DC not supported\n"); > + return -EINVAL; > + } > + > struct cxl_dax_region *cxlr_dax __free(put_cxl_dax_region) = > cxl_dax_region_alloc(cxlr); > if (IS_ERR(cxlr_dax)) > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c > index 95aee2a037fb..b0c2162b5e37 100644 > --- a/drivers/dax/bus.c > +++ b/drivers/dax/bus.c > @@ -181,6 +181,11 @@ static bool is_static(struct dax_region *dax_region) > return (dax_region->res.flags & IORESOURCE_DAX_STATIC) != 0; > } > > +static bool is_dynamic(struct dax_region *dax_region) > +{ > + return (dax_region->res.flags & IORESOURCE_DAX_DCD) != 0; > +} > + > bool static_dev_dax(struct dev_dax *dev_dax) > { > return is_static(dev_dax->region); > @@ -304,6 +309,9 @@ static unsigned long long dax_region_avail_size(struct dax_region *dax_region) > > lockdep_assert_held(&dax_region_rwsem); > > + if (is_dynamic(dax_region)) > + return 0; > + > for_each_dax_region_resource(dax_region, res) > size -= resource_size(res); > return size; > @@ -1389,6 +1397,8 @@ static umode_t dev_dax_visible(struct kobject *kobj, struct attribute *a, int n) > return 0; > if (a == &dev_attr_mapping.attr && is_static(dax_region)) > return 0; > + if (a == &dev_attr_mapping.attr && is_dynamic(dax_region)) > + return 0; > if ((a == &dev_attr_align.attr || > a == &dev_attr_size.attr) && is_static(dax_region)) > return 0444; > diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h > index 5909171a4428..6e739bfab932 100644 > --- a/drivers/dax/bus.h > +++ b/drivers/dax/bus.h > @@ -15,6 +15,7 @@ struct dax_region; > /* dax bus specific ioresource flags */ > #define IORESOURCE_DAX_STATIC BIT(0) > #define IORESOURCE_DAX_KMEM BIT(1) > +#define IORESOURCE_DAX_DCD BIT(2) > > struct dax_region *alloc_dax_region(struct device *parent, int region_id, > struct range *range, int target_node, unsigned int align, > diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c > index 3ab39b77843d..f58fe992aa8d 100644 > --- a/drivers/dax/cxl.c > +++ b/drivers/dax/cxl.c > @@ -13,19 +13,32 @@ static int cxl_dax_region_probe(struct device *dev) > struct cxl_region *cxlr = cxlr_dax->cxlr; > struct dax_region *dax_region; > struct dev_dax_data data; > + resource_size_t dev_size; > + unsigned long flags; > > if (nid == NUMA_NO_NODE) > nid = memory_add_physaddr_to_nid(cxlr_dax->hpa_range.start); > > + if (cxlr->mode == CXL_PARTMODE_DYNAMIC_RAM_A) > + flags = IORESOURCE_DAX_DCD; > + else > + flags = IORESOURCE_DAX_KMEM; > + > dax_region = alloc_dax_region(dev, cxlr->id, &cxlr_dax->hpa_range, nid, > - PMD_SIZE, IORESOURCE_DAX_KMEM); > + PMD_SIZE, flags); > if (!dax_region) > return -ENOMEM; > > + if (cxlr->mode == CXL_PARTMODE_DYNAMIC_RAM_A) > + /* Add empty seed dax device */ > + dev_size = 0; > + else > + dev_size = range_len(&cxlr_dax->hpa_range); > + > data = (struct dev_dax_data) { > .dax_region = dax_region, > .id = -1, > - .size = range_len(&cxlr_dax->hpa_range), > + .size = dev_size, > .memmap_on_memory = true, > }; >