On Fri, 2018-08-03 at 16:06 +1000, Rashmica Gupta wrote:
> This patch allows the memory removed by memtrace to be readded to the
> kernel. So now you don't have to reboot your system to add the memory
> back to the kernel or to have a different amount of memory removed.
>
> Signed-off-by: Rashmica Gupta <rashmic...@gmail.com>
Tested-by: Michael Neuling <mi...@neuling.org>
> ---
> To remove 1GB from each node:
> echo 1073741824 > /sys/kernel/debug/powerpc/memtrace/enable
>
> To add this memory back and remove 2GB:
> echo 2147483648 > /sys/kernel/debug/powerpc/memtrace/enable
>
> To just re-add memory:
> echo 0 > /sys/kernel/debug/powerpc/memtrace/enable
Nice... thanks!
Mikey
>
>
> arch/powerpc/platforms/powernv/memtrace.c | 93 ++++++++++++++++++++++++++++
> ---
> 1 file changed, 86 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/memtrace.c
> b/arch/powerpc/platforms/powernv/memtrace.c
> index b99283df8584..51fe0862dcab 100644
> --- a/arch/powerpc/platforms/powernv/memtrace.c
> +++ b/arch/powerpc/platforms/powernv/memtrace.c
> @@ -206,8 +206,11 @@ static int memtrace_init_debugfs(void)
>
> snprintf(ent->name, 16, "%08x", ent->nid);
> dir = debugfs_create_dir(ent->name, memtrace_debugfs_dir);
> - if (!dir)
> + if (!dir) {
> + pr_err("Failed to create debugfs directory for node
> %d\n",
> + ent->nid);
> return -1;
> + }
>
> ent->dir = dir;
> debugfs_create_file("trace", 0400, dir, ent, &memtrace_fops);
> @@ -218,18 +221,94 @@ static int memtrace_init_debugfs(void)
> return ret;
> }
>
> +static int online_mem_block(struct memory_block *mem, void *arg)
> +{
> + return device_online(&mem->dev);
> +}
> +
> +/*
> + * Iterate through the chunks of memory we have removed from the kernel
> + * and attempt to add them back to the kernel.
> + */
> +static int memtrace_online(void)
> +{
> + int i, ret = 0;
> + struct memtrace_entry *ent;
> +
> + for (i = memtrace_array_nr - 1; i >= 0; i--) {
> + ent = &memtrace_array[i];
> +
> + /* We have onlined this chunk previously */
> + if (ent->nid == -1)
> + continue;
> +
> + /* Remove from io mappings */
> + if (ent->mem) {
> + iounmap(ent->mem);
> + ent->mem = 0;
> + }
> +
> + if (add_memory(ent->nid, ent->start, ent->size)) {
> + pr_err("Failed to add trace memory to node %d\n",
> + ent->nid);
> + ret += 1;
> + continue;
> + }
> +
> + /*
> + * If kernel isn't compiled with the auto online option
> + * we need to online the memory ourselves.
> + */
> + if (!memhp_auto_online) {
> + walk_memory_range(PFN_DOWN(ent->start),
> + PFN_UP(ent->start + ent->size - 1),
> + NULL, online_mem_block);
> + }
> +
> + /*
> + * Memory was added successfully so clean up references to it
> + * so on reentry we can tell that this chunk was added.
> + */
> + debugfs_remove_recursive(ent->dir);
> + pr_info("Added trace memory back to node %d\n", ent->nid);
> + ent->size = ent->start = ent->nid = -1;
> + }
> + if (ret)
> + return ret;
> +
> + /* If all chunks of memory were added successfully, reset globals */
> + kfree(memtrace_array);
> + memtrace_array = NULL;
> + memtrace_size = 0;
> + memtrace_array_nr = 0;
> + return 0;
> +
> +}
> +
> static int memtrace_enable_set(void *data, u64 val)
> {
> - if (memtrace_size)
> + uint64_t bytes;
> +
> + /*
> + * Don't attempt to do anything if size isn't aligned to a memory
> + * block or equal to zero.
> + */
> + bytes = memory_block_size_bytes();
> + if (val & (bytes - 1)) {
> + pr_err("Value must be aligned with 0x%llx\n", bytes);
> return -EINVAL;
> + }
>
> - if (!val)
> - return -EINVAL;
> + /* Re-add/online previously removed/offlined memory */
> + if (memtrace_size) {
> + if (memtrace_online())
> + return -EAGAIN;
> + }
>
> - /* Make sure size is aligned to a memory block */
> - if (val & (memory_block_size_bytes() - 1))
> - return -EINVAL;
> + if (!val)
> + return 0;
>
> + /* Offline and remove memory */
> if (memtrace_init_regions_runtime(val))
> return -EINVAL;
>
