linux-kernel - Re: Fix built-in early-load Intel microcode alignment

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Date:   Sat, 18 Jan 2020 12:10:40 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Jari Ruusu <jari.ruusu@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Fenghua Yu <fenghua.yu@...el.com>, johannes.berg@...el.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        linux-remoteproc@...r.kernel.org
Subject: Re: Fix built-in early-load Intel microcode alignment

On Tue 14 Jan 18:27 PST 2020, Luis Chamberlain wrote:

> On Mon, Jan 13, 2020 at 11:44:25AM -0800, Linus Torvalds wrote:
> > On Mon, Jan 13, 2020 at 7:47 AM Luis Chamberlain <mcgrof@...nel.org> wrote:
> > >
> > > So I'd like to determine first if we really need this. Then if so,
> > > either add a new global config option, and worst comes to worst
> > > figure out a way to do it per driver. I don't think we'd need it
> > > per driver.
> > 
> > I really don't think we need to have a config option for some small
> > alignment. Increasing the alignment unconditionally to 16 bytes won't
> > hurt anybody.
> 
> Since you are confident in that, then simply bumping it to 16 bytes
> seems fine by me.
> 
> > Now, whether there might be other firmware loaders that need even more
> > alignment, that might be an interesting question, and if such an
> > alignment would be _huge_ we might want to worry about actual memory
> > waste.
> 
> I can only envision waste being considered due to alignent for remote
> proc folks, who I *doubt* use the built-in stuff given the large size of
> their blobs... but since you never know, better poke. So I've CC'd them.
> 

I've not heard of anyone using built-in firmware with remoteproc, but as
you say firmware used with remoteproc is large. So I can't see there
being a problem of potentially wasting 8 bytes...

> > But 16-byte alignment for a fw blob? That's nothing.
> 
> Fine by me if we are sure it won't break anything and we hear no
> complaints by remote proc folks.
> 

Go for it.

Regards,
Bjorn