On Wed, Sep 29, 2021 at 11:07:30AM +0100, Daniel P. Berrangé wrote: > I'm not sure if we actually need the full driver or not for testing > purposes. The the GenID is just in memory somewhere, and the somewhere > is reported via ACPI table entry. For QEMU its easy as the data is > exposed via fw_cfg which can be read from sysfs directly without > even needing to look at ACPI entries to find it. Not sure how we > find it with VMWare/HyperV though. This still has the problem that qemu is mangling the vmgenid. Nevertheless, on qemu-6.1.0-5.fc36.x86_64 I added this to a Linux guest: <genid>11223344-5566-7788-99aa-bbccddeeff00</genid> which turned into: -device vmgenid,guid=11223344-5566-7788-99aa-bbccddeeff00,id=vmgenid0 Inside the guest: # ls /sys/firmware/qemu_fw_cfg/by_name/etc/vmgenid_guid/ -l total 0 -r--------. 1 root root 4096 Sep 29 11:16 key -r--------. 1 root root 4096 Sep 29 11:16 name -r--------. 1 root root 0 Sep 29 11:16 raw -r--------. 1 root root 4096 Sep 29 11:16 size # hexdump -C /sys/firmware/qemu_fw_cfg/by_name/etc/vmgenid_guid/raw 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000020 00 00 00 00 00 00 00 00 44 33 22 11 66 55 88 77 |........D3".fU.w| 00000030 99 aa bb cc dd ee ff 00 00 00 00 00 00 00 00 00 |................| 00000040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00001000 But I think what I really need to do is look at the raw physical address: # hexdump -C /sys/firmware/qemu_fw_cfg/by_name/etc/vmgenid_addr/raw 00000000 28 f0 ff 7f 00 00 00 00 |(.......| 00000008 # dd if=/dev/mem bs=1 skip=$(( 0x7ffff028 )) count=16 | hexdump -C 16+0 records in 16+0 records out 16 bytes copied, 6.0392e-05 s, 265 kB/s 00000000 44 33 22 11 66 55 88 77 99 aa bb cc dd ee ff 00 |D3".fU.w........| 00000010 I think for VMware I'm really going to need the kernel driver, unless there's some way that iasl can be used to extract the information? Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org
