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To: Gregory Price , linux-cxl@vger.kernel.org Cc: nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org, kernel-team@meta.com, dan.j.williams@intel.com, vishal.l.verma@intel.com, dave.jiang@intel.com References: <20250321180731.568460-1-gourry@gourry.net> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20250321180731.568460-1-gourry@gourry.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 21.03.25 19:07, Gregory Price wrote: > Device capacity intended for use as system ram should be aligned to the > architecture-defined memory block size or that capacity will be silently > truncated and capacity stranded. > > As hotplug dax memory becomes more prevelant, the memory block size > alignment becomes more important for platform and device vendors to > pay attention to - so this truncation should not be silent. > > This issue is particularly relevant for CXL Dynamic Capacity devices, > whose capacity may arrive in spec-aligned but block-misaligned chunks. > > Example: > [...] kmem dax0.0: dax region truncated 2684354560 bytes - alignment > [...] kmem dax1.0: dax region truncated 1610612736 bytes - alignment > > Signed-off-by: Gregory Price > --- > drivers/dax/kmem.c | 18 ++++++++++++++---- > 1 file changed, 14 insertions(+), 4 deletions(-) > > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c > index e97d47f42ee2..15b6807b703d 100644 > --- a/drivers/dax/kmem.c > +++ b/drivers/dax/kmem.c > @@ -28,7 +28,8 @@ static const char *kmem_name; > /* Set if any memory will remain added when the driver will be unloaded. */ > static bool any_hotremove_failed; > > -static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r) > +static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r, > + unsigned long *truncated) > { > struct dev_dax_range *dax_range = &dev_dax->ranges[i]; > struct range *range = &dax_range->range; > @@ -41,6 +42,9 @@ static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r) > r->end = range->end; > return -ENOSPC; > } > + > + if (truncated && (r->start != range->start || r->end != range->end)) > + *truncated = (r->start - range->start) + (range->end - r->end); > return 0; > } > > @@ -75,6 +79,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) > mhp_t mhp_flags; > int numa_node; > int adist = MEMTIER_DEFAULT_DAX_ADISTANCE; > + unsigned long ttl_trunc = 0; > > /* > * Ensure good NUMA information for the persistent memory. > @@ -97,7 +102,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) > for (i = 0; i < dev_dax->nr_range; i++) { > struct range range; > > - rc = dax_kmem_range(dev_dax, i, &range); > + rc = dax_kmem_range(dev_dax, i, &range, NULL); > if (rc) { > dev_info(dev, "mapping%d: %#llx-%#llx too small after alignment\n", > i, range.start, range.end); > @@ -130,8 +135,9 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) > for (i = 0; i < dev_dax->nr_range; i++) { > struct resource *res; > struct range range; > + unsigned long truncated = 0; > > - rc = dax_kmem_range(dev_dax, i, &range); > + rc = dax_kmem_range(dev_dax, i, &range, &truncated); > if (rc) > continue; > > @@ -180,8 +186,12 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) > continue; > goto err_request_mem; > } > + > + ttl_trunc += truncated; > mapped++; > } > + if (ttl_trunc) > + dev_warn(dev, "dax region truncated %ld bytes - alignment\n", ttl_trunc); > > dev_set_drvdata(dev, data); > > @@ -216,7 +226,7 @@ static void dev_dax_kmem_remove(struct dev_dax *dev_dax) > struct range range; > int rc; > > - rc = dax_kmem_range(dev_dax, i, &range); > + rc = dax_kmem_range(dev_dax, i, &range, NULL); > if (rc) > continue; > Can't that be done a bit simpler? diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c index e97d47f42ee2e..23a68ff809cdf 100644 --- a/drivers/dax/kmem.c +++ b/drivers/dax/kmem.c @@ -67,8 +67,8 @@ static void kmem_put_memory_types(void) static int dev_dax_kmem_probe(struct dev_dax *dev_dax) { + unsigned long total_len = 0, orig_len = 0; struct device *dev = &dev_dax->dev; - unsigned long total_len = 0; struct dax_kmem_data *data; struct memory_dev_type *mtype; int i, rc, mapped = 0; @@ -97,6 +97,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) for (i = 0; i < dev_dax->nr_range; i++) { struct range range; + orig_len += range_len(&dev_dax->ranges[i].range); rc = dax_kmem_range(dev_dax, i, &range); if (rc) { dev_info(dev, "mapping%d: %#llx-%#llx too small after alignment\n", @@ -109,6 +110,9 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) if (!total_len) { dev_warn(dev, "rejecting DAX region without any memory after alignment\n"); return -EINVAL; + } else if (total_len != orig_len) { + dev_warn(dev, "DAX region truncated by %lu bytes due to alignment\n", + orig_len - total_len); } init_node_memory_type(numa_node, mtype); -- Cheers, David / dhildenb