Re: [PATCH v2] hw/i386: place setup_data at fixed place in memory

[Daniel P . Berrangé]

On Thu, Aug 04, 2022 at 02:03:29PM +0200, Jason A. Donenfeld wrote:
> Hi Daniel,
> 
> On Thu, Aug 04, 2022 at 10:25:36AM +0100, Daniel P. Berrangé wrote:
> > Yep, and ultimately the inability to distinguish UEFI vs other firmware
> > is arguably correct by design, as the QEMU <-> firmware interface is
> > supposed to be arbitrarily pluggable for any firmware implementation
> > not  limited to merely UEFI + seabios.
> 
> Indeed, I agree with this.
> 
> > 
> > > For now I suggest either reverting the original patch, or at least not
> > > enabling the knob by default for any machine types. In particular, when
> > > using MicroVM, the user must leave the knob disabled when direct booting
> > > a kernel on OVMF, and the user may or may not enable the knob when
> > > direct booting a kernel on SeaBIOS.
> > 
> > Having it opt-in via a knob would defeat Jason's goal of having the seed
> > available automatically.
> 
> Yes, adding a knob is absolutely out of the question.
> 
> It also doesn't actually solve the problem: this triggers when QEMU
> passes a DTB too. It's not just for the new RNG seed thing. This bug
> isn't new.

In the other thread I also mentioned that this RNG Seed addition has
caused a bug with AMD SEV too, making boot measurement attestation
fail because the kernel blob passed to the firmware no longer matches
what the tenant expects, due to the injected seed.

With regards,
Daniel
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