On Wed, Aug 04, 2010 at 09:50:55AM -0500, Anthony Liguori wrote: > On 08/04/2010 09:38 AM, Gleb Natapov wrote: > >> > >>But even if it wasn't it can potentially create havoc. I think we > >>currently believe that the northbridge likely never forwards RAM > >>access to a device so this doesn't fit how hardware would work. > >> > >Good point. > > > >>More importantly, BIOSes and ROMs do very funny things with RAM. > >>It's not unusual for a ROM to muck with the e820 map to allocate RAM > >>for itself which means there's always the chance that we're going to > >>walk over RAM being used for something else. > >> > >ROM does not muck with the e820. It uses PMM to allocate memory and the > >memory it gets is marked as reserved in e820 map. > > PMM allocations are only valid during the init function's execution. > It's intention is to enable the use of scratch memory to decompress > or otherwise modify the ROM to shrink its size. > Hm, may be. I read seabios code differently, but may be I misread it. > If a ROM needs memory after the init function, it needs to use the > traditional tricks to allocate long term memory and the most popular > one is modifying the e820 tables. > e820 has no in memory format, > See src/arch/i386/firmware/pcbios/e820mangler.S in gPXE. so this ugly code intercepts int15 and mangle result. OMG. How this can even work if more then two ROMs want to do that? -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
