[PATCH v2 11/12] virtio-mem: support CONFIG_PROC_VMCORE_DEVICE_RAM

David Hildenbrand
2024-12-04T12:55:24Z

Let's implement the get_device_ram() vmcore callback, so
architectures that select NEED_PROC_VMCORE_NEED_DEVICE_RAM, like s390
soon, can include that memory in a crash dump.

Merge ranges, and process ranges that might contain a mixture of plugged
and unplugged, to reduce the total number of ranges.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
drivers/virtio/virtio_mem.c | 88 +++++++++++++++++++++++++++++++++++++
fs/proc/Kconfig | 1 +
2 files changed, 89 insertions(+)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 73477d5b79cf..8a294b9cbcf6 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -2728,6 +2728,91 @@ static bool virtio_mem_vmcore_pfn_is_ram(struct vmcore_cb *cb,
mutex_unlock(&vm->hotplug_mutex);
return is_ram;
}
+
+#ifdef CONFIG_PROC_VMCORE_DEVICE_RAM
+static int virtio_mem_vmcore_add_device_ram(struct virtio_mem *vm,
+ struct list_head *list, uint64_t start, uint64_t end)
+{
+ int rc;
+
+ rc = vmcore_alloc_add_range(list, start, end - start);
+ if (rc)
+ dev_err(&vm->vdev->dev,
+ "Error adding device RAM range: %d\n", rc);
+ return rc;
+}
+
+static int virtio_mem_vmcore_get_device_ram(struct vmcore_cb *cb,
+ struct list_head *list)
+{
+ struct virtio_mem *vm = container_of(cb, struct virtio_mem,
+ vmcore_cb);
+ const uint64_t device_start = vm->addr;
+ const uint64_t device_end = vm->addr + vm->usable_region_size;
+ uint64_t chunk_size, cur_start, cur_end, plugged_range_start = 0;
+ LIST_HEAD(tmp_list);
+ int rc;
+
+ if (!vm->plugged_size)
+ return 0;
+
+ /* Process memory sections, unless the device block size is bigger. */
+ chunk_size = max_t(uint64_t, PFN_PHYS(PAGES_PER_SECTION),
+ vm->device_block_size);
+
+ mutex_lock(&vm->hotplug_mutex);
+
+ /*
+ * We process larger chunks and indicate the complete chunk if any
+ * block in there is plugged. This reduces the number of pfn_is_ram()
+ * callbacks and mimic what is effectively being done when the old
+ * kernel would add complete memory sections/blocks to the elfcore hdr.
+ */
+ cur_start = device_start;
+ for (cur_start = device_start; cur_start < device_end; cur_start = cur_end) {
+ cur_end = ALIGN_DOWN(cur_start + chunk_size, chunk_size);
+ cur_end = min_t(uint64_t, cur_end, device_end);
+
+ rc = virtio_mem_send_state_request(vm, cur_start,
+ cur_end - cur_start);
+
+ if (rc < 0) {
+ dev_err(&vm->vdev->dev,
+ "Error querying block states: %d\n", rc);
+ goto out;
+ } else if (rc != VIRTIO_MEM_STATE_UNPLUGGED) {
+ /* Merge ranges with plugged memory. */
+ if (!plugged_range_start)
+ plugged_range_start = cur_start;
+ continue;
+ }
+
+ /* Flush any plugged range. */
+ if (plugged_range_start) {
+ rc = virtio_mem_vmcore_add_device_ram(vm, &tmp_list,
+ plugged_range_start,
+ cur_start);
+ if (rc)
+ goto out;
+ plugged_range_start = 0;
+ }
+ }
+
+ /* Flush any plugged range. */
+ if (plugged_range_start)
+ rc = virtio_mem_vmcore_add_device_ram(vm, &tmp_list,
+ plugged_range_start,
+ cur_start);
+out:
+ mutex_unlock(&vm->hotplug_mutex);
+ if (rc < 0) {
+ vmcore_free_ranges(&tmp_list);
+ return rc;
+ }
+ list_splice_tail(&tmp_list, list);
+ return 0;
+}
+#endif /* CONFIG_PROC_VMCORE_DEVICE_RAM */
#endif /* CONFIG_PROC_VMCORE */

static int virtio_mem_init_kdump(struct virtio_mem *vm)
@@ -2737,6 +2822,9 @@ static int virtio_mem_init_kdump(struct virtio_mem *vm)
#ifdef CONFIG_PROC_VMCORE
dev_info(&vm->vdev->dev, "memory hot(un)plug disabled in kdump kernel\n");
vm->vmcore_cb.pfn_is_ram = virtio_mem_vmcore_pfn_is_ram;
+#ifdef CONFIG_PROC_VMCORE_DEVICE_RAM
+ vm->vmcore_cb.get_device_ram = virtio_mem_vmcore_get_device_ram;
+#endif /* CONFIG_PROC_VMCORE_DEVICE_RAM */
register_vmcore_cb(&vm->vmcore_cb);
return 0;
#else /* CONFIG_PROC_VMCORE */
diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig
index 5668620ab34d..6ae966c561e7 100644
--- a/fs/proc/Kconfig
+++ b/fs/proc/Kconfig
@@ -67,6 +67,7 @@ config NEED_PROC_VMCORE_DEVICE_RAM
config PROC_VMCORE_DEVICE_RAM
def_bool y
depends on PROC_VMCORE && NEED_PROC_VMCORE_DEVICE_RAM
+ depends on VIRTIO_MEM
help
If the elfcore hdr is allocated and prepared by the dump kernel
("2nd kernel") instead of the crashed kernel, RAM provided by memory
--
2.47.1