[PATCH v3 3/3] efi: Show the location of the bounce buffer

[Heinrich Schuchardt]

Am 2. September 2024 00:22:59 MESZ schrieb Simon Glass <sjg at chromium.org>:
>The EFI_LOADER_BOUNCE_BUFFER feature was added many years ago. It is not
>clear whether it is still needed, but 24 boards (lx2160ardb_tfa_stmm,
>lx2162aqds_tfa_SECURE_BOOT and the like) use it.
>
>This feature uses EFI page allocation to create a 64MB buffer 'in space'
>without any knowledge of where boards intend to load their images. This
>may result in image corruption or other problems.
>
>For example, if the feature is enabled on qemu_arm64 it puts the EFI
>bounce buffer at 1045MB, with the kernel at 1028MB and the ramdisk at
>1088MB. The kernel is probably smaller than 27MB but the buffer does
>overlap the ramdisk.
>
>The solution is probably to use BOUNCE_BUFFER instead, with the EFI
>version being dropped. For now, show the address of the EFI bounce
>buffer so people have a better chance to detect the problem.
>
>Note: I avoided converting this #ifdef to use IS_ENABLED() since I hope
>that the feature may be removed.

The functionality is still needed. A warning is of little use: what should the user do about it? The region should be reserved in LMB.

Best regards

Heinrich


>
>Signed-off-by: Simon Glass <sjg at chromium.org>
>---
>
>(no changes since v2)
>
>Changes in v2:
>- Drop patch 'Show more information in efi index'
>- Drop patch 'Avoid pool allocation in efi_get_memory_map_alloc()'
>- Add the word 'warning', use log_warning() and show the end address
>
> lib/efi_loader/efi_bootbin.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
>diff --git a/lib/efi_loader/efi_bootbin.c b/lib/efi_loader/efi_bootbin.c
>index 5bb0fdcf75d..9779dc09b5e 100644
>--- a/lib/efi_loader/efi_bootbin.c
>+++ b/lib/efi_loader/efi_bootbin.c
>@@ -211,6 +211,15 @@ efi_status_t efi_binary_run(void *image, size_t size, void *fdt)
> 		return -1;
> 	}
> 
>+#ifdef CONFIG_EFI_LOADER_BOUNCE_BUFFER
>+	/*
>+	 * Add a warning about this buffer, since it may conflict with other
>+	 * things
>+	 */
>+	log_warning("Warning: EFI bounce buffer %p-%p\n", efi_bounce_buffer,
>+		    efi_bounce_buffer + EFI_LOADER_BOUNCE_BUFFER_SIZE);
>+#endif
>+
> 	ret = efi_install_fdt(fdt);
> 	if (ret != EFI_SUCCESS)
> 		return ret;