Exposing the option to specify the second hard disk as a slave

[cshung]

Fix #353
This allows a second hard disk to be connected as a slave.

[copy]

Did you test this? For example, by booting up an OS from one hard drive and accessing a filesystem on the other? IIRC this was not working when I tested it some time ago, and I would prefer not to expose a broken feature.

[cshung]

Yes, I got xv6 working on v86.

As an educational OS, it oversimplifies things. The key thing it does is that it puts the kernel on a whole disk, and has the file system work on another (so that the bootloader don't need to understand the file system). That is why I needed a second disk.

With this change and a few changes on the xv6 side (mostly to get around the fact that lapic does not work), I got it to work to the point that ls and cat work to access the file system on the other disk.

xv6's file access is done through PIO, therefore my tests do not cover the DMA capabilities. If there is a bug with DMA, I wouldn't know.

[cshung]

Check this out to see it running:
https://www.youtube.com/watch?v=bCFhfRemzOw

[copy]

@cshung Very cool, thanks!

[onriv]

@cshung super cool~ any tutorial to boot xv6 plz?

[cshung]

@cshung super cool~ any tutorial to boot xv6 plz?

Check out my blog post to see what I did to get it to work.

[onriv]

@cshung super cool~ any tutorial to boot xv6 plz?

Check out my blog post to see what I did to get it to work.

I boot it up too (using your version of xv6 and the newest v86), but still got some messages like "spurious interrupt at xxxxxxx". I havent check the reason for this yet.