Re: [PATCH v12 1/5] efi: ARM/arm64: ignore DT memory nodes instead of removing them
From: Mark Rutland <hidden>
Date: 2016-02-23 11:58:16
Also in:
linux-arm-kernel, linux-efi, lkml
Hi, On Mon, Feb 22, 2016 at 05:58:19PM -0800, David Daney wrote:
From: Ard Biesheuvel <redacted> There are two problems with the UEFI stub DT memory node removal routine: - it deletes nodes as it traverses the tree, which happens to work but is not supported, as deletion invalidates the node iterator; - deleting memory nodes entirely may discard annotations in the form of additional properties on the nodes. Since the discovery of DT memory nodes occurs strictly before the UEFI init sequence, we can simply clear the memblock memory table before parsing the UEFI memory map. This way, it is no longer necessary to remove the nodes, so we can remove that logic from the stub as well.
This is a little bit scary, but I guess this works. My only concern is that when we get kexec, a subsequent kernel must also have EFI memory map support, or things go bad for the next EFI-aware kernel after that (as things like the runtime services may have been corrupted by the kernel in the middle). It's difficult to fix the general case later. A different option would be to support status="disabled" for the memory nodes, and ignore these in early_init_dt_scan_memory. That way a kernel cannot use memory without first having parsed the EFI memory map, and we can still get NUMA info from the disabled nodes. You'd still need a new kernel to take into account status, but at least we'd know all kernels would avoid using RAM that potentially needs to be preserved. Ard, Rob, thoughts? Mark.
quoted hunk ↗ jump to hunk
Signed-off-by: Ard Biesheuvel <redacted> Signed-off-by: David Daney <david.daney-YGCgFSpz5w/QT0dZR+AlfA@public.gmane.org> --- drivers/firmware/efi/arm-init.c | 8 ++++++++ drivers/firmware/efi/libstub/fdt.c | 24 +----------------------- 2 files changed, 9 insertions(+), 23 deletions(-)diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c index 9e15d57..40c9d85 100644 --- a/drivers/firmware/efi/arm-init.c +++ b/drivers/firmware/efi/arm-init.c@@ -143,6 +143,14 @@ static __init void reserve_regions(void) if (efi_enabled(EFI_DBG)) pr_info("Processing EFI memory map:\n"); + /* + * Discard memblocks discovered so far: if there are any at this + * point, they originate from memory nodes in the DT, and UEFI + * uses its own memory map instead. + */ + memblock_dump_all(); + memblock_remove(0, ULLONG_MAX); + for_each_efi_memory_desc(&memmap, md) { paddr = md->phys_addr; npages = md->num_pages;diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c index cf7b7d4..9df1560 100644 --- a/drivers/firmware/efi/libstub/fdt.c +++ b/drivers/firmware/efi/libstub/fdt.c@@ -24,7 +24,7 @@ efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt, unsigned long map_size, unsigned long desc_size, u32 desc_ver) { - int node, prev, num_rsv; + int node, num_rsv; int status; u32 fdt_val32; u64 fdt_val64;@@ -54,28 +54,6 @@ efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt, goto fdt_set_fail; /* - * Delete any memory nodes present. We must delete nodes which - * early_init_dt_scan_memory may try to use. - */ - prev = 0; - for (;;) { - const char *type; - int len; - - node = fdt_next_node(fdt, prev, NULL); - if (node < 0) - break; - - type = fdt_getprop(fdt, node, "device_type", &len); - if (type && strncmp(type, "memory", len) == 0) { - fdt_del_node(fdt, node); - continue; - } - - prev = node; - } - - /* * Delete all memory reserve map entries. When booting via UEFI, * kernel will use the UEFI memory map to find reserved regions. */-- 1.8.3.1