RE: [PATCH] crypto: inside-secure - Fix corruption on not fully coherent systems

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> -----Original Message-----
> From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Sent: Thursday, September 24, 2020 2:36 PM
> To: Van Leeuwen, Pascal <pvanleeuwen@xxxxxxxxxx>
> Cc: linux-crypto@xxxxxxxxxxxxxxx; antoine.tenart@xxxxxxxxxxx; davem@xxxxxxxxxxxxx; Ard Biesheuvel <ardb@xxxxxxxxxx>
> Subject: Re: [PATCH] crypto: inside-secure - Fix corruption on not fully coherent systems
>
> <<< External Email >>>
> On Thu, Sep 24, 2020 at 08:08:12AM +0000, Van Leeuwen, Pascal wrote:
> >
> > The fact that kmalloc uses it does _not_ rule out the fact that it wastes memory ...
> > And as long as you use kmalloc for fairly large data structures, it shouldn't matter much.
> > But here I need a couple of fairly small buffers.
>
> Those small buffers are embedded in a structure that's already
> aligned by kmalloc.  So just put your buffers at the start of
> the struct to minimise holes.
>
If you would make them fixed in size, then putting them at the start instead of the
end would indeed by a bit more efficient (but obviously, that doesn't work if you
dynamically scale them), I'll remember that.

But you still have 2 potential gaps (from buffer 1 to buffer 2 and from buffer 2 to
the other items in the struct) that are larger then they may need to be.
If everyone can live with the wasted space, it's fine by me. (frankly, I don't know
where these structs may end up - guess not on the minimal kernel stack then?)

I only did it this way  because I anticipated that that would be accepted ... guess I
could've save myself some trouble there :-)

Regards,
Pascal van Leeuwen
Silicon IP Architect Multi-Protocol Engines, Rambus Security
Rambus ROTW Holding BV
+31-73 6581953

Note: The Inside Secure/Verimatrix Silicon IP team was recently acquired by Rambus.
Please be so kind to update your e-mail address book with my new e-mail address.

> Cheers,
> --
> Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt


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