Laszlo Ersek <lersek@xxxxxxxxxx> writes: ... >>> >>> First, see my comments on the KVM patch. >>> >>> Second, ram_size is not the right thing to compare. What should be >>> checked is whether the highest guest-physical address that maps to RAM >>> can be represented in the address width of the host processor (and only >>> if EPT is enabled, but that sub-condition belongs to the KVM patch). >>> >>> Note that this is not the same as the check written in the patch. For >>> example, if you assume a 32-bit PCI hole with size 1 GB, then a total >>> guest RAM of size 63 GB will result in the highest guest-phys memory >>> address being 0xF_FFFF_FFFF, which just fits into 36 bits. >>> >>> Correspondingly, the above code would not print the warning for >>> >>> -m $((63 * 1024 + 1)) >>> >>> on my laptop (which has "address sizes : 36 bits physical, ..."), even >>> though such a guest would not boot for me (with EPT enabled). >>> >>> Please see >>> >>> http://thread.gmane.org/gmane.comp.bios.tianocore.devel/15418/focus=15447 >>> >>> So, "ram_size" in the controlling expression should be replaced with >>> "maximum_guest_ram_address" (which should be inclusive, and the <= relop >>> should be preserved). >> also with memory hotplug tuned on we should check if the end of >> hotplug memory area is less then limit, i.e.: >> >> pcms->hotplug_memory.base + hotplug_mem_size < 1ULL << max_phys_bits > > Seems reasonable, thanks for the hint! Thanks Igor and Laszlo, makes sense. I am wondering if this 1GB PCI hole is always fixed so that I can simply include that in calculating the maximum guest ram address ? Or do we have to figure that out every time ? > (The LHS in this instance is exclusive though, so equality should *not* > trigger the warning. "maximum_guest_ram_address" is inclusive, and > equality should trigger the warning. (Although equality seems quite > impossible in practice.)) > > Thanks! > Laszlo -- 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
