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[PATCH] efidisk: pass buffers with higher alignment
From: |
Stefan Agner |
Subject: |
[PATCH] efidisk: pass buffers with higher alignment |
Date: |
Thu, 5 May 2022 15:54:15 +0200 |
Despite the UEFI specification saying "the requirement is that the
start address of a buffer must be evenly divisible by IoAlign with
no remainder.", it seems that a higher alignment requirement is
neecssary on some system (e.g. a Intel NUC system with NVMe SSD).
That particular system has IoAlign set to 2, and sometimes returns
status 7 when buffers with alignment of 2 are passed. Things seem
to work fine with buffers aligned to 4 bytes.
It seems that IoAlign > 1 means 2 ^ IoAlign. There is also such a hint
in an example printed in the Driver Writer's Guide:
ScsiPassThruMode.IoAlign = 2; // Data must be alligned on 4-byte boundary
Pass 2 ^ IoAlign aligned buffers to make sure GRUB2 works properly on
all systems.
Note: The problem has only noticed with compressed squashfs. It seems
that ext4 (and presumably other file system drivers) pass buffers with
a higher alignment already.
Signed-off-by: Stefan Agner <stefan@agner.ch>
---
grub-core/disk/efi/efidisk.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/grub-core/disk/efi/efidisk.c b/grub-core/disk/efi/efidisk.c
index f077b5f55..0fc2f0826 100644
--- a/grub-core/disk/efi/efidisk.c
+++ b/grub-core/disk/efi/efidisk.c
@@ -553,8 +553,16 @@ grub_efidisk_readwrite (struct grub_disk *disk,
grub_disk_addr_t sector,
d = disk->data;
bio = d->block_io;
- /* Set alignment to 1 if 0 specified */
- io_align = bio->media->io_align ? bio->media->io_align : 1;
+ /*
+ * If IoAlign is > 1, it means alignment by 2^IoAlign
+ * Note: UEFI spec claims alignment by IoAlign. But there are systems
+ * with IoAlign=2 which return status 7 if 2 bytes aligned buffers are
+ * passed.
+ */
+ if (bio->media->io_align > 1)
+ io_align = 1 << bio->media->io_align;
+ else
+ io_align = 1;
num_bytes = size << disk->log_sector_size;
if ((grub_addr_t) buf & (io_align - 1))
--
2.36.0
- [PATCH] efidisk: pass buffers with higher alignment,
Stefan Agner <=