Re: [PATCH v2 2/2] efi: arm-stub: Round up FDT allocation to mapping size

Jeffrey Hugo
2017-02-12T20:10:56Z

On 2/9/2017 2:42 PM, Ard Biesheuvel wrote:
> The FDT is mapped via a fixmap entry that is at least 2 MB in size and
> 2 MB aligned on 4 KB page size kernels.
>
> On UEFI systems, the FDT allocation may share this 2 MB block with a
> reserved region, or another memory region that we should never map,
> unless we account for this in the size of the allocation (the alignment
> is already 2 MB)
>
> So instead of taking guesses at the needed space, simply allocate 2 MB
> immediately. The allocation will be recorded as a EFI_LOADER_DATA, and
> the kernel only memblock_reserve()'s the actual size of the FDT, so the
> unused space will be released to the kernel.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> ---

Reviewed-By: Jeffrey Hugo <jhugo-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>

> arch/arm64/include/asm/efi.h | 1 +
> drivers/firmware/efi/libstub/fdt.c | 57 +++++++++-----------
> 2 files changed, 25 insertions(+), 33 deletions(-)
>
> diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
> index 342e90d6d204..f642565fc1d0 100644
> --- a/arch/arm64/include/asm/efi.h
> +++ b/arch/arm64/include/asm/efi.h
> @@ -1,6 +1,7 @@
> #ifndef _ASM_EFI_H
> #define _ASM_EFI_H
>
> +#include <asm/boot.h>
> #include <asm/cpufeature.h>
> #include <asm/io.h>
> #include <asm/mmu_context.h>
> diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
> index 260c4b4b492e..41f457be64e8 100644
> --- a/drivers/firmware/efi/libstub/fdt.c
> +++ b/drivers/firmware/efi/libstub/fdt.c
> @@ -206,6 +206,10 @@ static efi_status_t exit_boot_func(efi_system_table_t *sys_table_arg,
> return update_fdt_memmap(p->new_fdt_addr, map);
> }
>
> +#ifndef MAX_FDT_SIZE
> +#define MAX_FDT_SIZE SZ_2M
> +#endif
> +
> /*
> * Allocate memory for a new FDT, then add EFI, commandline, and
> * initrd related fields to the FDT. This routine increases the
> @@ -233,7 +237,6 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
> u32 desc_ver;
> unsigned long mmap_key;
> efi_memory_desc_t *memory_map, *runtime_map;
> - unsigned long new_fdt_size;
> efi_status_t status;
> int runtime_entry_count = 0;
> struct efi_boot_memmap map;
> @@ -262,41 +265,29 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
> "Exiting boot services and installing virtual address map...\n");
>
> map.map = &memory_map;
> + status = efi_high_alloc(sys_table, MAX_FDT_SIZE, EFI_FDT_ALIGN,
> + new_fdt_addr, max_addr);
> + if (status != EFI_SUCCESS) {
> + pr_efi_err(sys_table,
> + "Unable to allocate memory for new device tree.\n");
> + goto fail;
> + }
> +
> /*
> - * Estimate size of new FDT, and allocate memory for it. We
> - * will allocate a bigger buffer if this ends up being too
> - * small, so a rough guess is OK here.
> + * Now that we have done our final memory allocation (and free)
> + * we can get the memory map key needed for exit_boot_services().
> */
> - new_fdt_size = fdt_size + EFI_PAGE_SIZE;
> - while (1) {
> - status = efi_high_alloc(sys_table, new_fdt_size, EFI_FDT_ALIGN,
> - new_fdt_addr, max_addr);
> - if (status != EFI_SUCCESS) {
> - pr_efi_err(sys_table, "Unable to allocate memory for new device tree.\n");
> - goto fail;
> - }
> -
> - status = update_fdt(sys_table,
> - (void *)fdt_addr, fdt_size,
> - (void *)*new_fdt_addr, new_fdt_size,
> - cmdline_ptr, initrd_addr, initrd_size);
> + status = efi_get_memory_map(sys_table, &map);
> + if (status != EFI_SUCCESS)
> + goto fail_free_new_fdt;
>
> - /* Succeeding the first time is the expected case. */
> - if (status == EFI_SUCCESS)
> - break;
> + status = update_fdt(sys_table, (void *)fdt_addr, fdt_size,
> + (void *)*new_fdt_addr, MAX_FDT_SIZE, cmdline_ptr,
> + initrd_addr, initrd_size);
>
> - if (status == EFI_BUFFER_TOO_SMALL) {
> - /*
> - * We need to allocate more space for the new
> - * device tree, so free existing buffer that is
> - * too small.
> - */
> - efi_free(sys_table, new_fdt_size, *new_fdt_addr);
> - new_fdt_size += EFI_PAGE_SIZE;
> - } else {
> - pr_efi_err(sys_table, "Unable to construct new device tree.\n");
> - goto fail_free_new_fdt;
> - }
> + if (status != EFI_SUCCESS) {
> + pr_efi_err(sys_table, "Unable to construct new device tree.\n");
> + goto fail_free_new_fdt;
> }
>
> priv.runtime_map = runtime_map;
> @@ -340,7 +331,7 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
> pr_efi_err(sys_table, "Exit boot services failed.\n");
>
> fail_free_new_fdt:
> - efi_free(sys_table, new_fdt_size, *new_fdt_addr);
> + efi_free(sys_table, MAX_FDT_SIZE, *new_fdt_addr);
>
> fail:
> sys_table->boottime->free_pool(runtime_map);
>

--
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.