Hey Peter, Philippe, On Fri, Dec 6, 2019 at 5:35 PM Philippe Mathieu-Daudé <phi...@redhat.com> wrote:
> On 12/6/19 3:27 PM, Peter Maydell wrote: > > On Mon, 2 Dec 2019 at 21:10, Niek Linnenbank <nieklinnenb...@gmail.com> > wrote: > >> > >> The Security Identifier device in Allwinner H3 System on Chip > >> gives applications a per-board unique identifier. This commit > >> adds support for the Allwinner H3 Security Identifier using > >> randomized data as input. > > > > If this is a fixed value in hardware, I'm not sure that > > having the QEMU model pick a random value is the best > > choice. If we just set it to a fixed value in QEMU, is > > that going to cause problems? > > > > (Generally it's nice for QEMU to be deterministic, so it > > behaves the same way every time you run it. Also if it's > > always the same we don't need to bother migrating the > > ID value.) > > Agreed. Since the identifier is 128-bit, I'd use DEFINE_PROP_UUID() or, > to be even safer, DEFINE_PROP_UUID_NODEFAULT(). > See how the ipmi-bmc-sim device checks its guid field and fails if unset. > Thank you both for clarifying this. OK, I'll update this patch such that the identifier is fixed, using the functions Philippe suggested. The reason I originally chose to make it randomized is that U-Boot mainline reads out the SID data in order to create a MAC address for the ethernet device. So when a user runs multiple QEMU machines inside a virtualized network, they will get the same MACs if the SID isnt unique. However this problem can also be solved very easy with U-Boot itself by just overriding the ethaddr environment variable. For your interest, in the U-Boot source you can see this behaviour in the file arch/arm/mach-sunxi/cpu_info.c:139 in sunxi_get_sid(), sun8i_efuse_read() where it reads the SID and in board/sunxi/board.c:782 in setup_environment() where it uses the SID to create the MAC address. Regards, Niek -- Niek Linnenbank
