Re: [PATCH v16 1/6] efi: ARM/arm64: ignore DT memory nodes instead of removing them

[Steve Capper <steve.capper@arm.com>]

On Thu, Apr 14, 2016 at 01:10:35PM +0200, Ard Biesheuvel wrote:
> On 14 April 2016 at 13:02, Steve Capper <steve.capper@arm.com> wrote:
> > On Fri, Apr 08, 2016 at 03:50:23PM -0700, 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.
> >>
> >> 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 aa1f743..5d6945b 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);
> >> +
> >
> > Does this change need to be applied to any other architectures given
> > that deletion code has been removed from libstub below?
> >
> 
> The 'generic' libstub code below is only used by ARM, so we're safe
> here in that regard.

Thanks Ard,
In that case, FWIW:
Acked-by: Steve Capper <steve.capper@arm.com>

Cheers,
-- 
Steve

> 
> 
> >>       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 6dba78a..e58abfa 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
> >>
> >>
> >> _______________________________________________
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> >> linux-arm-kernel@lists.infradead.org
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> >>
>