1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2001-2008 Silicon Graphics, Inc.  All rights reserved.
4  *
5  * A simple uncached page allocator using the generic allocator. This
6  * allocator first utilizes the spare (spill) pages found in the EFI
7  * memmap and will then start converting cached pages to uncached ones
8  * at a granule at a time. Node awareness is implemented by having a
9  * pool of pages per node.
10  */
11 
12 #include <linux/types.h>
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/init.h>
16 #include <linux/errno.h>
17 #include <linux/string.h>
18 #include <linux/efi.h>
19 #include <linux/nmi.h>
20 #include <linux/genalloc.h>
21 #include <linux/gfp.h>
22 #include <linux/pgtable.h>
23 #include <asm/efi.h>
24 #include <asm/page.h>
25 #include <asm/pal.h>
26 #include <linux/atomic.h>
27 #include <asm/tlbflush.h>
28 
29 struct uncached_pool {
30 	struct gen_pool *pool;
31 	struct mutex add_chunk_mutex;	/* serialize adding a converted chunk */
32 	int nchunks_added;		/* #of converted chunks added to pool */
33 	atomic_t status;		/* smp called function's return status*/
34 };
35 
36 #define MAX_CONVERTED_CHUNKS_PER_NODE	2
37 
38 struct uncached_pool uncached_pools[MAX_NUMNODES];
39 
40 
uncached_ipi_visibility(void * data)41 static void uncached_ipi_visibility(void *data)
42 {
43 	int status;
44 	struct uncached_pool *uc_pool = (struct uncached_pool *)data;
45 
46 	status = ia64_pal_prefetch_visibility(PAL_VISIBILITY_PHYSICAL);
47 	if ((status != PAL_VISIBILITY_OK) &&
48 	    (status != PAL_VISIBILITY_OK_REMOTE_NEEDED))
49 		atomic_inc(&uc_pool->status);
50 }
51 
52 
uncached_ipi_mc_drain(void * data)53 static void uncached_ipi_mc_drain(void *data)
54 {
55 	int status;
56 	struct uncached_pool *uc_pool = (struct uncached_pool *)data;
57 
58 	status = ia64_pal_mc_drain();
59 	if (status != PAL_STATUS_SUCCESS)
60 		atomic_inc(&uc_pool->status);
61 }
62 
63 
64 /*
65  * Add a new chunk of uncached memory pages to the specified pool.
66  *
67  * @pool: pool to add new chunk of uncached memory to
68  * @nid: node id of node to allocate memory from, or -1
69  *
70  * This is accomplished by first allocating a granule of cached memory pages
71  * and then converting them to uncached memory pages.
72  */
uncached_add_chunk(struct uncached_pool * uc_pool,int nid)73 static int uncached_add_chunk(struct uncached_pool *uc_pool, int nid)
74 {
75 	struct page *page;
76 	int status, i, nchunks_added = uc_pool->nchunks_added;
77 	unsigned long c_addr, uc_addr;
78 
79 	if (mutex_lock_interruptible(&uc_pool->add_chunk_mutex) != 0)
80 		return -1;	/* interrupted by a signal */
81 
82 	if (uc_pool->nchunks_added > nchunks_added) {
83 		/* someone added a new chunk while we were waiting */
84 		mutex_unlock(&uc_pool->add_chunk_mutex);
85 		return 0;
86 	}
87 
88 	if (uc_pool->nchunks_added >= MAX_CONVERTED_CHUNKS_PER_NODE) {
89 		mutex_unlock(&uc_pool->add_chunk_mutex);
90 		return -1;
91 	}
92 
93 	/* attempt to allocate a granule's worth of cached memory pages */
94 
95 	page = __alloc_pages_node(nid,
96 				GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
97 				IA64_GRANULE_SHIFT-PAGE_SHIFT);
98 	if (!page) {
99 		mutex_unlock(&uc_pool->add_chunk_mutex);
100 		return -1;
101 	}
102 
103 	/* convert the memory pages from cached to uncached */
104 
105 	c_addr = (unsigned long)page_address(page);
106 	uc_addr = c_addr - PAGE_OFFSET + __IA64_UNCACHED_OFFSET;
107 
108 	/*
109 	 * There's a small race here where it's possible for someone to
110 	 * access the page through /dev/mem halfway through the conversion
111 	 * to uncached - not sure it's really worth bothering about
112 	 */
113 	for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
114 		SetPageUncached(&page[i]);
115 
116 	flush_tlb_kernel_range(uc_addr, uc_addr + IA64_GRANULE_SIZE);
117 
118 	status = ia64_pal_prefetch_visibility(PAL_VISIBILITY_PHYSICAL);
119 	if (status == PAL_VISIBILITY_OK_REMOTE_NEEDED) {
120 		atomic_set(&uc_pool->status, 0);
121 		smp_call_function(uncached_ipi_visibility, uc_pool, 1);
122 		if (atomic_read(&uc_pool->status))
123 			goto failed;
124 	} else if (status != PAL_VISIBILITY_OK)
125 		goto failed;
126 
127 	preempt_disable();
128 
129 	flush_icache_range(uc_addr, uc_addr + IA64_GRANULE_SIZE);
130 
131 	/* flush the just introduced uncached translation from the TLB */
132 	local_flush_tlb_all();
133 
134 	preempt_enable();
135 
136 	status = ia64_pal_mc_drain();
137 	if (status != PAL_STATUS_SUCCESS)
138 		goto failed;
139 	atomic_set(&uc_pool->status, 0);
140 	smp_call_function(uncached_ipi_mc_drain, uc_pool, 1);
141 	if (atomic_read(&uc_pool->status))
142 		goto failed;
143 
144 	/*
145 	 * The chunk of memory pages has been converted to uncached so now we
146 	 * can add it to the pool.
147 	 */
148 	status = gen_pool_add(uc_pool->pool, uc_addr, IA64_GRANULE_SIZE, nid);
149 	if (status)
150 		goto failed;
151 
152 	uc_pool->nchunks_added++;
153 	mutex_unlock(&uc_pool->add_chunk_mutex);
154 	return 0;
155 
156 	/* failed to convert or add the chunk so give it back to the kernel */
157 failed:
158 	for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
159 		ClearPageUncached(&page[i]);
160 
161 	free_pages(c_addr, IA64_GRANULE_SHIFT-PAGE_SHIFT);
162 	mutex_unlock(&uc_pool->add_chunk_mutex);
163 	return -1;
164 }
165 
166 
167 /*
168  * uncached_alloc_page
169  *
170  * @starting_nid: node id of node to start with, or -1
171  * @n_pages: number of contiguous pages to allocate
172  *
173  * Allocate the specified number of contiguous uncached pages on the
174  * requested node. If not enough contiguous uncached pages are available
175  * on the requested node, roundrobin starting with the next higher node.
176  */
uncached_alloc_page(int starting_nid,int n_pages)177 unsigned long uncached_alloc_page(int starting_nid, int n_pages)
178 {
179 	unsigned long uc_addr;
180 	struct uncached_pool *uc_pool;
181 	int nid;
182 
183 	if (unlikely(starting_nid >= MAX_NUMNODES))
184 		return 0;
185 
186 	if (starting_nid < 0)
187 		starting_nid = numa_node_id();
188 	nid = starting_nid;
189 
190 	do {
191 		if (!node_state(nid, N_HIGH_MEMORY))
192 			continue;
193 		uc_pool = &uncached_pools[nid];
194 		if (uc_pool->pool == NULL)
195 			continue;
196 		do {
197 			uc_addr = gen_pool_alloc(uc_pool->pool,
198 						 n_pages * PAGE_SIZE);
199 			if (uc_addr != 0)
200 				return uc_addr;
201 		} while (uncached_add_chunk(uc_pool, nid) == 0);
202 
203 	} while ((nid = (nid + 1) % MAX_NUMNODES) != starting_nid);
204 
205 	return 0;
206 }
207 EXPORT_SYMBOL(uncached_alloc_page);
208 
209 
210 /*
211  * uncached_free_page
212  *
213  * @uc_addr: uncached address of first page to free
214  * @n_pages: number of contiguous pages to free
215  *
216  * Free the specified number of uncached pages.
217  */
uncached_free_page(unsigned long uc_addr,int n_pages)218 void uncached_free_page(unsigned long uc_addr, int n_pages)
219 {
220 	int nid = paddr_to_nid(uc_addr - __IA64_UNCACHED_OFFSET);
221 	struct gen_pool *pool = uncached_pools[nid].pool;
222 
223 	if (unlikely(pool == NULL))
224 		return;
225 
226 	if ((uc_addr & (0XFUL << 60)) != __IA64_UNCACHED_OFFSET)
227 		panic("uncached_free_page invalid address %lx\n", uc_addr);
228 
229 	gen_pool_free(pool, uc_addr, n_pages * PAGE_SIZE);
230 }
231 EXPORT_SYMBOL(uncached_free_page);
232 
233 
234 /*
235  * uncached_build_memmap,
236  *
237  * @uc_start: uncached starting address of a chunk of uncached memory
238  * @uc_end: uncached ending address of a chunk of uncached memory
239  * @arg: ignored, (NULL argument passed in on call to efi_memmap_walk_uc())
240  *
241  * Called at boot time to build a map of pages that can be used for
242  * memory special operations.
243  */
uncached_build_memmap(u64 uc_start,u64 uc_end,void * arg)244 static int __init uncached_build_memmap(u64 uc_start, u64 uc_end, void *arg)
245 {
246 	int nid = paddr_to_nid(uc_start - __IA64_UNCACHED_OFFSET);
247 	struct gen_pool *pool = uncached_pools[nid].pool;
248 	size_t size = uc_end - uc_start;
249 
250 	touch_softlockup_watchdog();
251 
252 	if (pool != NULL) {
253 		memset((char *)uc_start, 0, size);
254 		(void) gen_pool_add(pool, uc_start, size, nid);
255 	}
256 	return 0;
257 }
258 
259 
uncached_init(void)260 static int __init uncached_init(void)
261 {
262 	int nid;
263 
264 	for_each_online_node(nid) {
265 		uncached_pools[nid].pool = gen_pool_create(PAGE_SHIFT, nid);
266 		mutex_init(&uncached_pools[nid].add_chunk_mutex);
267 	}
268 
269 	efi_memmap_walk_uc(uncached_build_memmap, NULL);
270 	return 0;
271 }
272 
273 __initcall(uncached_init);
274