On 06/09/2016 12:48, Chao Peng wrote: >> As you might expect, I don't agree with removing the >> firmware. There's >> room for much more optimization before duplicating firmware code in >> QEMU. I'd rather see numbers for: >> >> 1) qboot optimizations: adopt the fw_cfg DMA interface instead of the >> cbfs flash hack (so that -kernel works), drop PCI bridge >> initialization, copy less than 64K of memory from ROM to 0xf0000; > > I can do the evaluation on qboot. Also adding Amnon Ilan, to see if > there is some thing we can do for SeaBios.
For SeaBIOS we can try dropping PAM and PCI, but not much more. I've pushed fw_cfg DMA support and some PAM optimizations to qboot (it doesn't setup PAM if QEMU doesn't configure 0xf0000-0x100000 as ROM). I've left it for you to figure out which parts of PCI initialization can be removed. >> 2) Linux optimizations: using an uncompressed image to avoid the >> cost of copying and decompressing. QEMU can already load the image >> at the right place and the real mode stub can do little more than >> GDT/IDT setup. > > This works surely. I actually followed your suggestion in v1 to make > kernel multiboot-compatible and then load that kernel in QEMU directly Please try posting the multiboot patches to the upstream x86 Linux mailing list. I am very interested in them, because I think it's the simplest way to compare qboot with direct kernel load. And as you say, it might make patch 11 a little smaller and possibly more acceptable. Paolo
