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[2003:cb:c733:7c00:d067:e327:4f99:7546]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-431bd9aa83asm16969125e9.31.2024.10.30.03.25.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 30 Oct 2024 03:25:36 -0700 (PDT) Message-ID: <55df76a9-afa3-4dc0-a7f9-ff9b6f139448@redhat.com> Date: Wed, 30 Oct 2024 11:25:33 +0100 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 1/3] memory: implement memory_block_advise/probe_max_size To: Gregory Price , x86@kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org Cc: linux-cxl@vger.kernel.org, Jonathan.Cameron@huawei.com, dan.j.williams@intel.com, rrichter@amd.com, Terry.Bowman@amd.com, dave.jiang@intel.com, ira.weiny@intel.com, alison.schofield@intel.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, rafael@kernel.org, lenb@kernel.org, osalvador@suse.de, gregkh@linuxfoundation.org, akpm@linux-foundation.org, rppt@kernel.org References: <20241029202041.25334-1-gourry@gourry.net> <20241029202041.25334-2-gourry@gourry.net> From: David Hildenbrand 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: <20241029202041.25334-2-gourry@gourry.net> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 29.10.24 21:20, Gregory Price wrote: > Hotplug memory sources may have opinions on what the memblock size > should be - usually for alignment purposes. For example, CXL memory > extents can be 256MB with a matching alignment. If this size/alignment > is smaller than the block size, it can result in stranded capacity. > > Implement memory_block_advise_max_size for use prior to allocator init, > for software to advise the system on the max block size. > > Implement memory_block_probe_max_size for use by arch init code to > calculate the best block size. Use of advice is architecture defined. > > The probe value can never change after first probe. Calls to advise > after probe will return -EBUSY to aid debugging. > > On systems without hotplug, always return -ENODEV and 0 respectively. > > Suggested-by: Ira Weiny > Signed-off-by: Gregory Price > --- > drivers/base/memory.c | 48 ++++++++++++++++++++++++++++++++++++++++++ > include/linux/memory.h | 10 +++++++++ > 2 files changed, 58 insertions(+) > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index 67858eeb92ed..099a972c52dc 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -110,6 +110,54 @@ static void memory_block_release(struct device *dev) > kfree(mem); > } > > +/** > + * memory_block_advise_max_size() - advise memory hotplug on the max suggested > + * block size, usually for alignment. > + * @size: suggestion for maximum block size. must be aligned on power of 2. > + * > + * Early boot software (pre-allocator init) may advise archs on the max block > + * size. This value can only decrease after initialization, as the intent is > + * to identify the largest supported alignment for all sources. > + * > + * Use of this value is arch-defined, as is min/max block size. > + * > + * Return: 0 on success > + * -EINVAL if size is 0 or not pow2 aligned > + * -EBUSY if value has already been probed > + */ > +static size_t memory_block_advised_sz; Nit: if everything is called "size", call this "size" as well. > +static bool memory_block_advised_size_queried; > +int memory_block_advise_max_size(size_t size) Not that memory_block_size_bytes() uses "unsigned long". I don't think it matters here. Or could it on 32bit? (I assume that code will not really matter on 32bit) > +{ > + if (!size || !is_power_of_2(size)) > + return -EINVAL; > + > + if (memory_block_advised_size_queried) > + return -EBUSY; > + > + if (memory_block_advised_sz) > + memory_block_advised_sz = min(size, memory_block_advised_sz); > + else > + memory_block_advised_sz = size; > + > + return 0; > +} > + > +/** > + * memory_block_advised_max_size() - query advised max hotplug block size. > + * > + * After the first call, the value can never change. Callers looking for the > + * actual block size should use memory_block_size_bytes. This interface is > + * intended for use by arch-init when initializing the hotplug block size. > + * > + * Return: advised size in bytes, or 0 if never set. > + */ > +size_t memory_block_advised_max_size(void) > +{ > + memory_block_advised_size_queried = true; > + return memory_block_advised_sz;> +} > + I wonder if both should.could be "__init" ? So they could only be called from __init ... which sounds like the tight thing to do? Acked-by: David Hildenbrand -- Cheers, David / dhildenb