On 09/07/2015 10:26, Laszlo Ersek wrote: >> > >> > Perhaps KVM could simply hide memory above the limit (i.e. treat it as >> > MMIO), and the BIOS could remove RAM above the limit from the e820 >> > memory map? > I'd prefer to leave the guest firmware*s* out of this... :) > > E820 is a legacy BIOS concept. In OVMF we'd have to hack the memory > resource descriptor HOBs (which in turn control the DXE memory space > map, which in turn controls the UEFI memory map). Those HOBs are > currently based on what the CMOS reports about the RAM available under > and above 4GB. > > It's pretty complex already (will get more complex with SMM support), > and TBH, for working around such an obscure issue, I wouldn't like to > complicate it even further... > > After all, this is a host platform limitation. The solution should be to > either move to a more capable host, or do it in software (disable EPT). The reason I mentioned the firmware is because you could in principle have the same issue on real hardware - say putting 128 GB on your laptop. The firmware should cope with it. If OVMF does not use etc/e820, it can instead hack the values it reads from CMOS, bounding them according to the CPUID value. Paolo -- 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
