On Fri, 1 Sept 2023 at 05:16, Ho, Tong <tong...@amd.com> wrote: > > Hi Richard, > > Thanks for your input. > > I have questions regarding using qemu/guest-random.h for QEMU device models. > > Using qemu/guest-random.h, how can this TRNG model ensure its independence > from > other uses of the same qemu_guest_getrandom() and qemu_guest_random_seed_*()? > > By "other uses", I mean components and/or devices using qemu/guest-random.h > but unrelated to this Xilinx Versal TRNG device. > > By "independent", I mean the Xilinx Versal TRNG device is: > > 1. Not impacted by other uses that may or may not need to set the '-seed' > option, and > > 2. Not impacting other uses just because a Xilinx Versal machine user decides > to use deterministic mode *only" for this TRNG device. > > Also, I am at a loss in how unrelated QEMU devices can remain independent > when: > > 3. qemu/guest-random.h uses '__thread' variable for GRand context, but > > 4. QEMU devices run mostly as co-routines and not as separate threads.
You shouldn't need to care about any of this. Just assume you can get decent quality random numbers from qemu_guest_getrandom() or qemu_guest_getrandom_nofail(). The -seed option is for the entire simulation, not specific to individual RNG devices. > I suppose the Versal TRNG implementation could use g_rand_*() directly, > having a GRand object in the device state and seeding through > g_rand_set_seed_array(). Don't do something non-standard. Write this RNG device the same way we do all other RNG devices in QEMU. thanks -- PMM
