Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > 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. Agreed, it's probably not a good idea to deviate too much from how real hardware would behave IMO. As a simplification of Paolo's idea, is it possible for qemu to completely ignore memory above the limit ? Will that break anything ? :) > 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
