[PATCH 2/2] v1 powerpc/powernv: Enable removal of memory for in memory tracing
Rashmica Gupta
rashmica.g at gmail.com
Fri Apr 28 15:42:27 AEST 2017
Some powerpc hardware features may want to gain access to a chunk of
undisturbed real memory. This update provides a means to unplug said memory
from the kernel with a set of debugfs calls. By writing an integer containing
the size of memory to be unplugged into
/sys/kernel/debug/powerpc/memtrace/enable, the code will remove that much
memory from the end of each available chip's memory space (ie each memory node).
In addition, the means to read out the contents of the unplugged memory is also
provided by reading out the /sys/kernel/debug/powerpc/memtrace/<chip-id>/trace
file.
Signed-off-by: Anton Blanchard <anton at samba.org>
Signed-off-by: Rashmica Gupta <rashmica.g at gmail.com>
---
This requires the 'Wire up hpte_removebolted for powernv' patch.
RFC -> v1: Added in two missing locks. Replaced the open-coded flush_memory_region() with the existing
flush_inval_dcache_range(start, end).
memtrace_offline_pages() is open-coded because offline_pages is designed to be
called through the sysfs interface - not directly.
We could move the offlining of pages to userspace, which removes some of this
open-coding. This would then require passing info to the kernel such that it
can then remove the memory that has been offlined. This could be done using
notifiers, but this isn't simple due to locking (remove_memory needs
mem_hotplug_begin() which the sysfs interface already has). This could also be
done through the debugfs interface (similar to what is done here). Either way,
this would require the process that needs the memory to have open-coded code
which it shouldn't really be involved with.
As the current remove_memory() function requires the memory to already be
offlined, it makes sense to keep the offlining and removal of memory
functionality grouped together so that a process can simply make one request to
unplug some memory. Ideally there would be a kernel function we could call that
would offline the memory and then remove it.
arch/powerpc/platforms/powernv/memtrace.c | 276 ++++++++++++++++++++++++++++++
1 file changed, 276 insertions(+)
create mode 100644 arch/powerpc/platforms/powernv/memtrace.c
diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c
new file mode 100644
index 0000000..86184b1
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/memtrace.c
@@ -0,0 +1,276 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * Copyright (C) IBM Corporation, 2014
+ *
+ * Author: Anton Blanchard <anton at au.ibm.com>
+ */
+
+#define pr_fmt(fmt) "powernv-memtrace: " fmt
+
+#include <linux/bitops.h>
+#include <linux/string.h>
+#include <linux/memblock.h>
+#include <linux/init.h>
+#include <linux/moduleparam.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/slab.h>
+#include <linux/memory.h>
+#include <linux/memory_hotplug.h>
+#include <asm/machdep.h>
+#include <asm/debugfs.h>
+#include <asm/cacheflush.h>
+
+struct memtrace_entry {
+ void *mem;
+ u64 start;
+ u64 size;
+ u32 nid;
+ struct dentry *dir;
+ char name[16];
+};
+
+static struct memtrace_entry *memtrace_array;
+static unsigned int memtrace_array_nr;
+
+static ssize_t memtrace_read(struct file *filp, char __user *ubuf,
+ size_t count, loff_t *ppos)
+{
+ struct memtrace_entry *ent = filp->private_data;
+
+ return simple_read_from_buffer(ubuf, count, ppos, ent->mem, ent->size);
+}
+
+static bool valid_memtrace_range(struct memtrace_entry *dev,
+ unsigned long start, unsigned long size)
+{
+ if ((dev->start <= start) &&
+ ((start + size) <= (dev->start + dev->size)))
+ return true;
+
+ return false;
+}
+
+static int memtrace_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+ unsigned long size = vma->vm_end - vma->vm_start;
+ struct memtrace_entry *dev = filp->private_data;
+
+ if (!valid_memtrace_range(dev, vma->vm_pgoff << PAGE_SHIFT, size))
+ return -EINVAL;
+
+ vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+ if (io_remap_pfn_range(vma, vma->vm_start,
+ vma->vm_pgoff + (dev->start >> PAGE_SHIFT),
+ size, vma->vm_page_prot))
+ return -EAGAIN;
+
+ return 0;
+}
+
+static const struct file_operations memtrace_fops = {
+ .llseek = default_llseek,
+ .read = memtrace_read,
+ .mmap = memtrace_mmap,
+ .open = simple_open,
+};
+
+static int check_memblock_online(struct memory_block *mem, void *arg)
+{
+ if (mem->state != MEM_ONLINE)
+ return -1;
+
+ return 0;
+}
+
+static int change_memblock_state(struct memory_block *mem, void *arg)
+{
+ unsigned long state = (unsigned long)arg;
+
+ mem->state = state;
+ return 0;
+}
+
+static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages)
+{
+ u64 end_pfn = start_pfn + nr_pages - 1;
+
+ if (walk_memory_range(start_pfn, end_pfn, NULL,
+ check_memblock_online))
+ return false;
+
+ walk_memory_range(start_pfn, end_pfn, (void *)MEM_GOING_OFFLINE,
+ change_memblock_state);
+
+ mem_hotplug_begin();
+ if (offline_pages(start_pfn, nr_pages)) {
+ walk_memory_range(start_pfn, end_pfn, (void *)MEM_ONLINE,
+ change_memblock_state);
+ mem_hotplug_done();
+ return false;
+ }
+
+ walk_memory_range(start_pfn, end_pfn, (void *)MEM_OFFLINE,
+ change_memblock_state);
+ mem_hotplug_done();
+
+ /* Clear the dcache to remove any references to the memory */
+ flush_inval_dcache_range((u64)__va(start_pfn << PAGE_SHIFT),
+ (u64)__va(end_pfn << PAGE_SHIFT));
+
+ /* Now remove memory from the mappings */
+ lock_device_hotplug();
+ remove_memory(nid, start_pfn << PAGE_SHIFT, nr_pages << PAGE_SHIFT);
+ unlock_device_hotplug();
+
+ return true;
+}
+
+static u64 memtrace_alloc_node(u32 nid, u64 size)
+{
+ u64 start_pfn, end_pfn, nr_pages;
+ u64 base_pfn;
+
+ if (!NODE_DATA(nid) || !node_spanned_pages(nid))
+ return 0;
+
+ start_pfn = node_start_pfn(nid);
+ end_pfn = node_end_pfn(nid);
+ nr_pages = size >> PAGE_SHIFT;
+
+ /* Trace memory needs to be aligned to the size */
+ end_pfn = round_down(end_pfn - nr_pages, nr_pages);
+
+ for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) {
+ if (memtrace_offline_pages(nid, base_pfn, nr_pages) == true)
+ return base_pfn << PAGE_SHIFT;
+ }
+
+ return 0;
+}
+
+static int memtrace_init_regions_runtime(u64 size)
+{
+ u64 m;
+ u32 nid;
+
+ memtrace_array = kzalloc(sizeof(struct memtrace_entry) *
+ num_online_nodes(), GFP_KERNEL);
+ if (!memtrace_array) {
+ pr_err("Failed to allocate memtrace_array\n");
+ return -EINVAL;
+ }
+
+ for_each_online_node(nid) {
+ m = memtrace_alloc_node(nid, size);
+ /*
+ * A node might not have any local memory, so warn but
+ * continue on.
+ */
+ if (!m) {
+ pr_err("Failed to allocate trace memory on node %d\n",
+ nid);
+ } else {
+ pr_info("Allocated trace memory on node %d at 0x%016llx\n",
+ nid, m);
+
+ memtrace_array[memtrace_array_nr].start = m;
+ memtrace_array[memtrace_array_nr].size = size;
+ memtrace_array[memtrace_array_nr].nid = nid;
+ memtrace_array_nr++;
+ }
+ }
+ return 0;
+}
+
+static struct dentry *memtrace_debugfs_dir;
+
+static int memtrace_init_debugfs(void)
+{
+ int ret = 0;
+ int i;
+
+ for (i = 0; i < memtrace_array_nr; i++) {
+ struct dentry *dir;
+ struct memtrace_entry *ent = &memtrace_array[i];
+
+ ent->mem = ioremap(ent->start, ent->size);
+ /* Warn but continue on */
+ if (!ent->mem) {
+ pr_err("Failed to map trace memory at 0x%llx\n",
+ ent->start);
+ ret = -1;
+ continue;
+ }
+
+ snprintf(ent->name, 16, "%08x", ent->nid);
+ dir = debugfs_create_dir(ent->name, memtrace_debugfs_dir);
+ if (!dir)
+ return -1;
+
+ ent->dir = dir;
+ debugfs_create_file("trace", 0400, dir, ent, &memtrace_fops);
+ debugfs_create_x64("start", 0400, dir, &ent->start);
+ debugfs_create_x64("size", 0400, dir, &ent->size);
+ debugfs_create_u32("node", 0400, dir, &ent->nid);
+ }
+
+ return ret;
+}
+
+static u64 memtrace_size;
+
+static int memtrace_enable_set(void *data, u64 val)
+{
+ if (memtrace_size)
+ return -EINVAL;
+
+ if (!val)
+ return -EINVAL;
+
+ /* Make sure size is aligned to a memory block */
+ if (val & (memory_block_size_bytes()-1))
+ return -EINVAL;
+
+ if (memtrace_init_regions_runtime(val))
+ return -EINVAL;
+
+ if (memtrace_init_debugfs())
+ return -EINVAL;
+
+ memtrace_size = val;
+
+ return 0;
+}
+
+static int memtrace_enable_get(void *data, u64 *val)
+{
+ *val = memtrace_size;
+ return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(memtrace_init_fops, memtrace_enable_get, memtrace_enable_set, "0x%016llx\n");
+
+static int memtrace_init(void)
+{
+ memtrace_debugfs_dir = debugfs_create_dir("memtrace", powerpc_debugfs_root);
+ if (!memtrace_debugfs_dir)
+ return -1;
+
+ debugfs_create_file("enable", 0600, memtrace_debugfs_dir,
+ NULL, &memtrace_init_fops);
+
+ return 0;
+}
+machine_device_initcall(powernv, memtrace_init);
+
--
2.9.3
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