On Fri, 6 Oct 2023 23:27:34 +0300 ValdikSS <i...@valdikss.org.ru> wrote:
> On 06.10.2023 21:33, Glenn Washburn wrote: > > This gives me more confidence in using 127, although its not clear to > > me without digging in the syslinux code that 127 is actually being > > used as the transfer size (or when it is). It appears to be a hard max > > transfer, which means the actual transfer size could be lower. In this > > series, we're using 127 as the transfer size always. So questions that > > would help clear that up are: where does MaxTransfer ultimately come > > from and when can it be less than 127? How is disk.maxtransfer used and > > when does it not represent the actual transfer size. > > I haven't studied syslinux code deeply, but it seems they have a > fallback code which decreases reading sector number on failures if > larger reads were unsuccessful. > GRUB just falls back to CHS reading if int13_extensions read failed. > > I've checked with seabios debugging capabilities in qemu. > > disk_op d=0x000f3a20 lba=6544 buf=0x00010000 count=127 cmd=2 > disk_op d=0x000f3a20 lba=6671 buf=0x00010000 count=127 cmd=2 > disk_op d=0x000f3a20 lba=6798 buf=0x00010000 count=127 cmd=2 > disk_op d=0x000f3a20 lba=6925 buf=0x00010000 count=127 cmd=2 > disk_op d=0x000f3a20 lba=7052 buf=0x00010000 count=127 cmd=2 > disk_op d=0x000f3a20 lba=7179 buf=0x00010000 count=127 cmd=2 > disk_op d=0x000f3a20 lba=7306 buf=0x00010000 count=127 cmd=2 > disk_op d=0x000f3a20 lba=7433 buf=0x00010000 count=127 cmd=2 > > > Ok, this lends more weight to not taking those values too seriously > > then. Do you have an explanation of how you got an MBR with sectors == > > 2? I would have a hard time believing that debian would produce that. > > That was just a regular automatic Debian installation in a VM on a 8GB > disk size. > Check the thread > https://lists.debian.org/debian-boot/2023/07/msg00043.html Strange, perhaps that's worth reporting as a bug to Debian. Glenn _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
