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[80.187.83.110]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46fa9d6fb41sm6808515e9.17.2025.10.07.13.07.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Oct 2025 13:07:45 -0700 (PDT) Message-ID: <4e832570-32f8-46a5-80d0-40570db862b2@redhat.com> Date: Tue, 7 Oct 2025 22:07:43 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/4] s390/sclp: Add support for dynamic (de)configuration of memory To: Sumanth Korikkar , Andrew Morton , linux-mm Cc: LKML , linux-s390 , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev References: <20250926131527.3260733-1-sumanthk@linux.ibm.com> <20250926131527.3260733-3-sumanthk@linux.ibm.com> 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20250926131527.3260733-3-sumanthk@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit [...] > --- > drivers/s390/char/sclp_mem.c | 291 +++++++++++++++++++++++++++++------ > 1 file changed, 241 insertions(+), 50 deletions(-) > > diff --git a/drivers/s390/char/sclp_mem.c b/drivers/s390/char/sclp_mem.c > index 27f49f5fd358..802439230294 100644 > --- a/drivers/s390/char/sclp_mem.c > +++ b/drivers/s390/char/sclp_mem.c > @@ -9,9 +9,12 @@ > #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt > > #include > +#include > #include > #include > #include > +#include > +#include > #include > #include > #include > @@ -27,7 +30,6 @@ > #define SCLP_CMDW_ASSIGN_STORAGE 0x000d0001 > #define SCLP_CMDW_UNASSIGN_STORAGE 0x000c0001 > > -static DEFINE_MUTEX(sclp_mem_mutex); > static LIST_HEAD(sclp_mem_list); > static u8 sclp_max_storage_id; > static DECLARE_BITMAP(sclp_storage_ids, 256); > @@ -38,6 +40,18 @@ struct memory_increment { > int standby; > }; > > +struct mblock { > + struct kobject kobj; > + unsigned int id; > + unsigned int memmap_on_memory; > + unsigned int config; > +}; > + > +struct memory_block_arg { > + struct mblock *mblocks; > + struct kset *kset; > +}; I would avoid using "memory_block_arg" as it reminds of core mm "struct memory_block". Similarly, I'd not call this "mblock". What about incorporating the "sclp" side of things? "struct sclp_mem" / "struct sclp_mem_arg" Nicely fits "sclp_mem.c" ;) Something like that might be better. > + > struct assign_storage_sccb { > struct sccb_header header; > u16 rn; > @@ -185,15 +199,11 @@ static int sclp_mem_notifier(struct notifier_block *nb, > { > unsigned long start, size; > struct memory_notify *arg; > - unsigned char id; > int rc = 0; > > arg = data; > start = arg->start_pfn << PAGE_SHIFT; > size = arg->nr_pages << PAGE_SHIFT; > - mutex_lock(&sclp_mem_mutex); > - for_each_clear_bit(id, sclp_storage_ids, sclp_max_storage_id + 1) > - sclp_attach_storage(id); > switch (action) { > case MEM_GOING_OFFLINE: > /* > @@ -204,45 +214,201 @@ static int sclp_mem_notifier(struct notifier_block *nb, > if (contains_standby_increment(start, start + size)) > rc = -EPERM; > break; Is there any reson this notifier is still needed? I'd assume we can just allow for offlining + re-onlining as we please now. In fact, I'd assume we can get rid of the notifier entirely now? > - case MEM_PREPARE_ONLINE: > - /* > - * Access the altmap_start_pfn and altmap_nr_pages fields > - * within the struct memory_notify specifically when dealing > - * with only MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE notifiers. > - * > - * When altmap is in use, take the specified memory range > - * online, which includes the altmap. > - */ > - if (arg->altmap_nr_pages) { > - start = PFN_PHYS(arg->altmap_start_pfn); > - size += PFN_PHYS(arg->altmap_nr_pages); > - } > - rc = sclp_mem_change_state(start, size, 1); > - if (rc || !arg->altmap_nr_pages) > - break; > - /* > - * Set CMMA state to nodat here, since the struct page memory > - * at the beginning of the memory block will not go through the > - * buddy allocator later. > - */ > - __arch_set_page_nodat((void *)__va(start), arg->altmap_nr_pages); > + default: > break; > - case MEM_FINISH_OFFLINE: > + } > + return rc ? NOTIFY_BAD : NOTIFY_OK; > +} > + > +static ssize_t config_mblock_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) > +{ > + struct mblock *mblock = container_of(kobj, struct mblock, kobj); > + > + return sysfs_emit(buf, "%u\n", READ_ONCE(mblock->config)); > +} > + > +static ssize_t config_mblock_store(struct kobject *kobj, struct kobj_attribute *attr, > + const char *buf, size_t count) > +{ > + unsigned long long addr, block_size; "unsigned long" should be sufficient I'm sure :) > + struct memory_block *mem; > + struct mblock *mblock; > + unsigned char id; > + bool value; > + int rc; > + > + rc = kstrtobool(buf, &value); > + if (rc) > + return rc; > + mblock = container_of(kobj, struct mblock, kobj); > + block_size = memory_block_size_bytes(); > + addr = mblock->id * block_size; > + /* > + * Hold device_hotplug_lock when adding/removing memory blocks. > + * Additionally, also protect calls to find_memory_block() and > + * sclp_attach_storage(). > + */ > + rc = lock_device_hotplug_sysfs(); > + if (rc) > + goto out; > + for_each_clear_bit(id, sclp_storage_ids, sclp_max_storage_id + 1) > + sclp_attach_storage(id); > + if (value) { > + if (mblock->config) > + goto out_unlock; > + rc = sclp_mem_change_state(addr, block_size, 1); > + if (rc) > + goto out_unlock; > /* > - * When altmap is in use, take the specified memory range > - * offline, which includes the altmap. > + * Set entire memory block CMMA state to nodat. Later, when > + * page tables pages are allocated via __add_memory(), those > + * regions are marked __arch_set_page_dat(). > */ > - if (arg->altmap_nr_pages) { > - start = PFN_PHYS(arg->altmap_start_pfn); > - size += PFN_PHYS(arg->altmap_nr_pages); > + __arch_set_page_nodat((void *)__va(addr), block_size >> PAGE_SHIFT); > + rc = __add_memory(0, addr, block_size, > + mblock->memmap_on_memory ? > + MHP_MEMMAP_ON_MEMORY | MHP_OFFLINE_INACCESSIBLE : MHP_NONE); > + if (rc) > + goto out_unlock; Do we have to undo the state change? > + mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(addr))); > + put_device(&mem->dev); > + WRITE_ONCE(mblock->config, 1); > + } else { > + if (!mblock->config) > + goto out_unlock; > + mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(addr))); > + if (mem->state != MEM_OFFLINE) { > + put_device(&mem->dev); > + rc = -EBUSY; > + goto out_unlock; > } > - sclp_mem_change_state(start, size, 0); > - break; > - default: > - break; > + /* drop the ref just got via find_memory_block() */ > + put_device(&mem->dev); > + sclp_mem_change_state(addr, block_size, 0); > + __remove_memory(addr, block_size); > + WRITE_ONCE(mblock->config, 0); > } > - mutex_unlock(&sclp_mem_mutex); > - return rc ? NOTIFY_BAD : NOTIFY_OK; > +out_unlock: > + unlock_device_hotplug(); > +out: > + return rc ? rc : count; > +} > + > +static ssize_t memmap_on_memory_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) > +{ > + struct mblock *mblock = container_of(kobj, struct mblock, kobj); > + > + return sysfs_emit(buf, "%u\n", READ_ONCE(mblock->memmap_on_memory)); > +} > + > +static ssize_t memmap_on_memory_store(struct kobject *kobj, struct kobj_attribute *attr, > + const char *buf, size_t count) > +{ > + unsigned long block_size; > + struct memory_block *mem; > + struct mblock *mblock; > + bool value; > + int rc; > + > + rc = kstrtobool(buf, &value); > + if (rc) > + return rc; > + rc = lock_device_hotplug_sysfs(); > + if (rc) > + return rc; > + block_size = memory_block_size_bytes(); > + mblock = container_of(kobj, struct mblock, kobj); > + mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(mblock->id * block_size))); > + if (!mem) { > + WRITE_ONCE(mblock->memmap_on_memory, value); > + } else { > + put_device(&mem->dev); > + rc = -EBUSY; > + } > + unlock_device_hotplug(); > + return rc ? rc : count; > +} > + > +static void mblock_sysfs_release(struct kobject *kobj) > +{ > + struct mblock *mblock = container_of(kobj, struct mblock, kobj); > + > + kfree(mblock); > +} > + > +static const struct kobj_type ktype = { > + .release = mblock_sysfs_release, > + .sysfs_ops = &kobj_sysfs_ops, > +}; > + > +static struct kobj_attribute memmap_attr = > + __ATTR(memmap_on_memory, 0644, memmap_on_memory_show, memmap_on_memory_store); > +static struct kobj_attribute config_attr = > + __ATTR(config, 0644, config_mblock_show, config_mblock_store); > + > +static struct attribute *mblock_attrs[] = { > + &memmap_attr.attr, > + &config_attr.attr, > + NULL, > +}; > + > +static struct attribute_group mblock_attr_group = { > + .attrs = mblock_attrs, > +}; > + > +static int create_mblock(struct mblock *mblock, struct kset *kset, > + unsigned int id, bool config, bool memmap_on_memory) > +{ > + int rc; > + > + mblock->memmap_on_memory = memmap_on_memory; > + mblock->config = config; > + mblock->id = id; > + kobject_init(&mblock->kobj, &ktype); > + rc = kobject_add(&mblock->kobj, &kset->kobj, "memory%d", id); > + if (rc) > + return rc; > + rc = sysfs_create_group(&mblock->kobj, &mblock_attr_group); > + if (rc) > + kobject_put(&mblock->kobj); > + return rc; > +} > + > +/* > + * Create /sys/firmware/memory/memoryX for boottime configured online memory > + * blocks > + */ > +static int create_online_mblock(struct memory_block *mem, void *argument) "online" is conusing. It's "initial" / "configured". Same applies to the other functions that mention "online". > +{ > + struct memory_block_arg *arg; > + struct mblock *mblocks; > + struct kset *kset; > + unsigned int id; > + > + id = mem->dev.id; > + arg = (struct memory_block_arg *)argument; > + mblocks = arg->mblocks; > + kset = arg->kset; > + return create_mblock(&mblocks[id], kset, id, true, false); > +} > + > +static int __init create_initial_online_mblocks(struct mblock *mblocks, struct kset *kset) > +{ > + struct memory_block_arg arg; > + > + arg.mblocks = mblocks; > + arg.kset = kset; > + return for_each_memory_block(&arg, create_online_mblock); > +} > + > +static struct mblock * __init allocate_mblocks(void) > +{ > + u64 max_mblocks; Nit: why an u64? The block ids are "unsigned int id;" > + u64 block_size; > + > + block_size = memory_block_size_bytes(); > + max_mblocks = roundup(sclp.rnmax * sclp.rzm, block_size) / block_size; > + return kcalloc(max_mblocks, sizeof(struct mblock), GFP_KERNEL); I think you should structure the code a bit differently, not splitting the function up into tiny helpers. static int __init init_sclp_mem(void) { const u64 block_size = memory_block_size_bytes(); const u64 max_mblocks = roundup(sclp.rnmax * sclp.rzm, block_size) / block_size; struct sclp_mem_arg arg; struct kset *kset; int rc; /* We'll allocate memory for all blocks ahead of time. */ sclp_mem = kcalloc(max_mblocks, sizeof(struct mblock), GFP_KERNEL); if (!sclp_mem) return -ENOMEM; kset = kset_create_and_add("memory", NULL, firmware_kobj); if (!kset) return -ENOMEM; /* Initial memory is in the "configured" state already. */ arg.sclp_mem = sclp_mem; arg.kset = kset; rc = for_each_memory_block(&arg, create_configured_sclp_mem); if (rc) return rc; /* Standby memory is "deconfigured". */ return create_standby_sclp_mem(sclp_mem, kset); } Should still be quite readable. > } > > static struct notifier_block sclp_mem_nb = { > @@ -264,14 +430,17 @@ static void __init align_to_block_size(unsigned long *start, > *size = size_align; > } > > -static void __init add_memory_merged(u16 rn) > +static int __init create_standby_mblocks_merged(struct mblock *mblocks, > + struct kset *kset, u16 rn) > { > unsigned long start, size, addr, block_size; > static u16 first_rn, num; > + unsigned int id; > + int rc = 0; > > if (rn && first_rn && (first_rn + num == rn)) { > num++; > - return; > + return rc; > } > if (!first_rn) > goto skip_add; > @@ -286,24 +455,31 @@ static void __init add_memory_merged(u16 rn) > if (!size) > goto skip_add; > for (addr = start; addr < start + size; addr += block_size) { > - add_memory(0, addr, block_size, > - cpu_has_edat1() ? > - MHP_MEMMAP_ON_MEMORY | MHP_OFFLINE_INACCESSIBLE : MHP_NONE); > + id = addr / block_size; > + rc = create_mblock(&mblocks[id], kset, id, false, mhp_supports_memmap_on_memory()); > + if (rc) > + break; > } > skip_add: > first_rn = rn; > num = 1; > + return rc; > } > > -static void __init sclp_add_standby_memory(void) > +static int __init create_standby_mblocks(struct mblock *mblocks, struct kset *kset) > { > struct memory_increment *incr; > + int rc = 0; > > list_for_each_entry(incr, &sclp_mem_list, list) { > if (incr->standby) > - add_memory_merged(incr->rn); > + rc = create_standby_mblocks_merged(mblocks, kset, incr->rn); > + if (rc) > + goto out; > } > - add_memory_merged(0); > + rc = create_standby_mblocks_merged(mblocks, kset, 0); > +out: > + return rc; > } > > static void __init insert_increment(u16 rn, int standby, int assigned) > @@ -336,10 +512,12 @@ static void __init insert_increment(u16 rn, int standby, int assigned) > list_add(&new_incr->list, prev); > } > > -static int __init sclp_detect_standby_memory(void) > +static int __init sclp_setup_memory(void) > { > struct read_storage_sccb *sccb; > int i, id, assigned, rc; > + struct mblock *mblocks; > + struct kset *kset; > > /* No standby memory in kdump mode */ > if (oldmem_data.start) Wouldn't we still want to create the ones for initial memory at least? [...] -- Cheers David / dhildenb