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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 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; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 55F291A0014 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: gr1ytaeknc6pio7c9hc3nsp8yciajfk9 X-HE-Tag: 1730283908-548485 X-HE-Meta: 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 3PU3ChzW h3Kvq5FQCz0ViOybdm96qbsJJUdaSbFMeHZwxSTXvwRNWRH3CwuH5FdESt5wHC0pJFAAA3xE+S4duMPNF3zOYRE9FJmkzSxDQ5fgVGBvpAb9uVWshSa8+hwxDcECGnwTmzo09Z9v2MZIdVL9JNs5aGjydlB+eMVsuz9oH16z8qYNLwxVk7CWvx+Q0v8XYKm+NkuiQ0V6go9E/rCT/8iOGSWk1X9Qnm/4akYIxhyceoE3F2YO1VphZICJHmSqFYyMOmrbMmUgAnjkHMauG2R9IFnI+CiMUbgmVWtRGT7Zv8j1d4G7l06pvl6v4LlsaT5p4d+6JfjDAM7z967GA2dtHJyR1WKooKw9k6Jd7UdhaC2ofICO7OFt4bGjV0jYqJs9E7qzX/D++osSfKTqVkkuMEsCDFyII22aD+FlYInWd9Ivntf3dZTpfLJq5GYCtDxFeAdF3jZbI9LUdrOnj1cLVJpdlKq610JdkwlRwQsyPJEunQfqH7B/kygvZuZ5itvUC+MKFuKK+JhmMB310zzzMn70rqlktsv6hdIJQZVJt3ijNFzU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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