On Tue, May 31, 2022 at 06:10:42PM +0200, Heinrich Schuchardt wrote: > On 5/31/22 17:53, Stefan Agner wrote: > > Some devices report IoAlign values but seem to require buffers with > > higher alignment. > > > > The UEFI specification is saying: "IoAlign values of 0 and 1 mean that > > the buffer can be placed anywhere in memory. Otherwise, IoAlign must > > be a power of 2, and the requirement is that the start address of a > > buffer must be evenly divisible by IoAlign with no remainder." > > > > Some devices report IoAlign of 2, however seem to require 4 bytes > > aligned buffers. It seems that this got misinterpreted by some vendors > > assuming IoAlign is 2^IoAlign. There is also such a hint in an example > > in earlier versions of the Driver Writer's Guide: > > ScsiPassThruMode.IoAlign = 2; // Data must be alligned on 4-byte boundary > > > > Some devices report no alignment requirements at all but seem to read > > corrupted data or report read errors when passing unaligned buffers. > > > > Work around by using an alignment of at least BlockSize (typically 512 > > bytes) in any case. If IoAlign (interpreted as per UEFI specification) > > requests a higher alignment than BlockSize, follow IoAlign still. > > > > 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 <ste...@agner.ch> > > Acked-by: Heinrich Schuchardt <heinrich.schucha...@canaonical.com>
Reviewed-by: Daniel Kiper <daniel.ki...@oracle.com> Daniel _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
