Rusty Russell wrote: >> fixmap-bootparam.patch >> > > While this would justify the above patch, it is IMHO, the wrong approach > for adding a paravirt module later: a module shouldn't fail to load > because you forgot a boot cmdline param. I really think a #ifdef > CONFIG_XXX_MODULE would be clearer. > We can't rely on a compile time kernel option - we really must have a boot parameter. This is not the wrong approach. If you forgot to add the boot parameter, so be it. You reboot and the paravirt module can load. The whole approach only makes sense if you can fully virtualize the kernel boot, so this is a completely plausible scenario. What we don't want to do is force Linux to have to move the fixmap at runtime. I think that could be very, very messy. Course, it may be possible (with a dynamic fixmap, it moves into that realm). But to completely remove the boot parameter without the ability to change the fixmap at runtime makes dynamic loading of a hypervisor module impossible. Besides, it is useful for testing the performance impact of reducing lowmem - which I don't think has been adequately benchmarked to this day, and is still an area of investigation. Zach
