Re: [Vol-users] Analyzing large KVM/libvrt dumps

Sébastien, Here is the physical memory block for an x64 Windows 7 SP1 Hyper-V VM that is equipped with 4 GiB of memory: 1: kd> dq nt!MmPhysicalMemoryBlock L1 fffff800`0290d038 fffffa83`007bbfc0 1: kd> dq /c1 fffffa83`007bbfc0 fffffa83`007bbfc0 00000000`00000003 NumberOfRanges fffffa83`007bbfc8 00000000`000fff8e NumberOfPages fffffa83`007bbfd0 00000000`00000001 StartingPFN fffffa83`007bbfd8 00000000`0000009e NumberOfPFNs fffffa83`007bbfe0 00000000`00000100 StartingPFN fffffa83`007bbfe8 00000000`000f7ef0 NumberOfPFNs fffffa83`007bbff0 00000000`00100000 StartingPFN fffffa83`007bbff8 00000000`00008000 NumberOfPFNs As you can see, the reserved areas are as follows: 0x00000000 - 0x00001000 0x0009f000 - 0x00100000 0xf7ff0000 - 0x100000000 Further detail may be obtained using the !arbiter command the results of which are displayed at the end of this mail. As you can see, only a small area is reserved for the virtual PCI bus. There is nothing that specifically requires that any space be reserved below 4 GiB. That has been the convention, but PC makers and VM vendors are free to make their own design decisions. And in some cases they do so, as can be seen. Obviously, the only sound way to reconstruct a systems physical memory space is if the metadata describing the space is stored along with the data bits. If you are working with a specific VM or PC you can make intelligent guesses, as you did with VMWare. However, generalizing those assumptions to other VMs and PCs is probably not going to work. Regards, George. 1: kd> !arbiter 2 DEVNODE fffffa83028a5b80 (HTREE\ROOT\0) Memory Arbiter "RootMemory" at fffff800028d89c0 Allocated ranges: 0000000000000000 - 000000000009ffff 0000000000000000 - 0000000000000fff C 00000000 <Not on bus> 0000000000000000 - 000000000009ffff CB fffffa83028d6bb0 00000000000a0000 - 00000000000bffff S fffffa8302962600 (pci) 00000000000c0000 - 00000000000dffff B fffffa83028d6bb0 00000000000e0000 - 00000000000fffff B fffffa83028d6bb0 0000000000100000 - 00000000f7ffffff B fffffa83028d6bb0 00000000f8000000 - 00000000fffbffff S fffffa8302962600 (pci) 00000000fffc0000 - 00000000ffffffff B fffffa83028d6bb0 0000000fe0000000 - 0000000fffefffff S fffffa8302962600 (pci) 0001000000000000 - ffffffffffffffff 00000000 <Not on bus> Possible allocation: < none > DEVNODE fffffa83028db710 (ACPI\PNP0A03\0) Memory Arbiter "PCI Memory (b=0)" at fffffa83028e0960 Allocated ranges: 0000000000000000 - 000000000009ffff 00000000 <Not on bus> 00000000000a0000 - 00000000000bffff S fffffa8303dc0480 00000000000c0000 - 00000000f7ffffff 00000000 <Not on bus> 00000000f8000000 - 00000000fbffffff fffffa83028e6a10 (s3cap) 00000000fec00000 - 00000000fec00fff 00000000fec00000 - 00000000fec003ff CB fffffa8302874e30 00000000fec00000 - 00000000fec00fff CBA fffffa83028ea060 00000000fee00000 - 00000000fee00fff 00000000fee00000 - 00000000fee003ff CB fffffa8302874e30 00000000fee00000 - 00000000fee00fff CBA fffffa83028ea060 00000000fffc0000 - 0000000fdfffffff 00000000 <Not on bus> 0000000fff700000 - 0000000fffefffff fffffa830293c6c0 (SynthVid) 0000000ffff00000 - ffffffffffffffff 0000000ffff00000 - ffffffffffffffff C 00000000 <Not on bus> 0001000000000000 - ffffffffffffffff C 00000000 <Not on bus> Possible allocation: < none >