Re: propagating vmgenid outward and upward

[Michael S. Tsirkin]

On Wed, Mar 02, 2022 at 05:32:07PM +0100, Jason A. Donenfeld wrote:
> Hi Michael,
> 
> On Wed, Mar 02, 2022 at 11:22:46AM -0500, Michael S. Tsirkin wrote:
> > > Because that 16 byte read of vmgenid is not atomic. Let's say you read
> > > the first 8 bytes, and then the VM is forked.
> > 
> > But at this point when VM was forked plaintext key and nonce are all in
> > buffer, and you previously indicated a fork at this point is harmless.
> > You wrote "If it changes _after_ that point of check ... it doesn't
> > matter:"
> 
> Ahhh, fair point. I think you're right.
> 
> Alright, so all we're talking about here is an ordinary 16-byte read,
> and 16 bytes of storage per keypair, and a 16-byte comparison.
> 
> Still seems much worse than just having a single word...
> 
> Jason

And it is, I saw a 30% higher overhead, it is however 30% of a very
low number ;)

-- 
MST