[PATCH v12 1/5] efi: ARM/arm64: ignore DT memory nodes instead of removing them

Mark Rutland
2016-02-23T11:58:05Z

Hi,

On Mon, Feb 22, 2016 at 05:58:19PM -0800, David Daney wrote:
> From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>
> 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.

> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Signed-off-by: David Daney <david.daney@cavium.com>
> ---
> 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
>