linux-kernel - Re: [PATCH v4 22/24] powerpc/pseries: Implement secvars for dynamic secure boot

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Date:   Wed, 01 Feb 2023 13:15:22 +1100
From:   Andrew Donnellan <ajd@...ux.ibm.com>
To:     Nicholas Piggin <npiggin@...il.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-integrity@...r.kernel.org
Cc:     sudhakar@...ux.ibm.com, bgray@...ux.ibm.com, erichte@...ux.ibm.com,
        gregkh@...uxfoundation.org, nayna@...ux.ibm.com,
        linux-kernel@...r.kernel.org, zohar@...ux.ibm.com,
        gjoyce@...ux.ibm.com, ruscur@...sell.cc, gcwilson@...ux.ibm.com,
        joel@....id.au
Subject: Re: [PATCH v4 22/24] powerpc/pseries: Implement secvars for dynamic
 secure boot

On Tue, 2023-01-31 at 18:55 +1000, Nicholas Piggin wrote:
> > > > +       var.datalen = 1;
> > > > +       var.data = kzalloc(1, GFP_KERNEL);
> > > 
> > > This could just point to a u8 on stack I think?
> > 
> > Until we get VMAP_STACK and we'll have to switch back.
> 
> AFAIKS plpks_read_var does not require linear map, so should not be
> required. IMO that's the right way to go for an external API, so
> actually plpks_write_var is the outlier there and should be changed
> to follow read and remove in not requiring special pointers.

Indeed, I was confused - in the read case, the buffer doesn't get
directly passed to the hcall.

I'll wait a little bit longer for more feedback on v5 of this series
and maybe fix this in v6 if mpe thinks I should respin it again.

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@...ux.ibm.com   IBM Australia Limited