Hi Tom,

> ELTORITO does NOT create a sector oriented device, accesible by the
> kernel (or LBACACHE). it can't be accessed by INT13  READ/WRITE
> functions and so can't be cached by LBACACHE.

The workflow is that the boot process activates ELTORITO mode
in the BIOS, which then creates an int 13 representation of
the bootable CD/DVD as 2048 byte per sector LBA drive. Then
the ELTORITO DOS driver uses int 13.42 to fetch CD/DVD sector
contents whenever SHSUCDX requests sector data from ELTORITO.

Because LBACACHE is an int 13 based cache with LBA support,
I see the risk that it will try to cache BIOS responses to
LBA int 13 requests from the ELTORITO driver, which causes
the risk that it returns WRONG data to ELTORITO when sectors
are read multiple times and the cache believes it can help,
while actually having cached only the first 512 bytes of the
cached CD/DVD sector data.

So LBACACHE does not know about the CDEX communications of
the ELTORITO driver with SHSUCDX, but it may intercept the
int 13 communications between the ELTORITO driver and BIOS.

https://github.com/chenall/grub4dos/blob/master/stage2/eltorito.asm

Regards, Eric



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