Message-ID: <1afe8de217d4436b6cdc91d65729c9baacff9274.camel@linux.ibm.com>
Subject: Re: [PATCH v4 22/24] powerpc/pseries: Implement secvars for dynamic
 secure boot
From:   Andrew Donnellan <ajd@linux.ibm.com>
To:     Nicholas Piggin <npiggin@gmail.com>, linuxppc-dev@lists.ozlabs.org,
        linux-integrity@vger.kernel.org
Cc:     sudhakar@linux.ibm.com, bgray@linux.ibm.com, erichte@linux.ibm.com,
        gregkh@linuxfoundation.org, nayna@linux.ibm.com,
        linux-kernel@vger.kernel.org, zohar@linux.ibm.com,
        gjoyce@linux.ibm.com, ruscur@russell.cc, gcwilson@linux.ibm.com,
        joel@jms.id.au
Date:   Wed, 01 Feb 2023 13:15:22 +1100
In-Reply-To: <CQ690JS6Q5RG.8KHL6V7BODI0@bobo>
References: <20230120074306.1326298-1-ajd@linux.ibm.com>
         <20230120074306.1326298-23-ajd@linux.ibm.com>
         <CQ05ZDYG6KNU.1G9O3ITQDIHEM@bobo>
         <9f16d86e855f22823ee24e6a6236a16556425f29.camel@linux.ibm.com>
         <CQ690JS6Q5RG.8KHL6V7BODI0@bobo>
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On Tue, 2023-01-31 at 18:55 +1000, Nicholas Piggin wrote:
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0var.datalen =3D 1;
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0var.data =3D kzalloc(1, =
GFP_KERNEL);
> > >=20
> > > This could just point to a u8 on stack I think?
> >=20
> > Until we get VMAP_STACK and we'll have to switch back.
>=20
> 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.

--=20
Andrew Donnellan    OzLabs, ADL Canberra
ajd@linux.ibm.com   IBM Australia Limited