Re: [PATCH v5 2/7] xen/arm: zynqmp: Forward plaform specific firmware calls

[Stefano Stabellini <sstabellini@kernel.org>]

On Tue, 11 Dec 2018, Julien Grall wrote:
> Hi Stefano,
> 
> On 11/12/2018 18:50, Stefano Stabellini wrote:
> > On Tue, 11 Dec 2018, Julien Grall wrote:
> > > Hi Stefano,
> > > 
> > > On 03/12/2018 21:03, Stefano Stabellini wrote:
> > > > From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
> > > > 
> > > > From: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> > > > 
> > > > Introduce zynqmp_eemi: a function responsible for implementing access
> > > > controls over the firmware calls. Only calls that are allowed are
> > > > forwarded to the firmware.
> > > > 
> > > > Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> > > > Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>
> > > > 
> > > > ---
> > > > Changes in v4:
> > > > - fix typo
> > > > - add header guard
> > > > - add emacs magic
> > > > - remove #includes that will only be used later
> > > > - add copyright notice to header
> > > > - remove SMCCC 1.1 check
> > > > ---
> > > >    xen/arch/arm/platforms/Makefile                    |  1 +
> > > >    xen/arch/arm/platforms/xilinx-zynqmp-eemi.c        | 34
> > > > ++++++++++++++++++++++
> > > >    xen/arch/arm/platforms/xilinx-zynqmp.c             | 11 +++++++
> > > >    xen/include/asm-arm/platforms/xilinx-zynqmp-eemi.h | 30
> > > > +++++++++++++++++++
> > > >    4 files changed, 76 insertions(+)
> > > >    create mode 100644 xen/arch/arm/platforms/xilinx-zynqmp-eemi.c
> > > >    create mode 100644 xen/include/asm-arm/platforms/xilinx-zynqmp-eemi.h
> > > > 
> > > > diff --git a/xen/arch/arm/platforms/Makefile
> > > > b/xen/arch/arm/platforms/Makefile
> > > > index a79bdb9..fe8e0c7 100644
> > > > --- a/xen/arch/arm/platforms/Makefile
> > > > +++ b/xen/arch/arm/platforms/Makefile
> > > > @@ -9,3 +9,4 @@ obj-y += sunxi.o
> > > >    obj-$(CONFIG_ARM_64) += thunderx.o
> > > >    obj-$(CONFIG_ARM_64) += xgene-storm.o
> > > >    obj-$(CONFIG_MPSOC_PLATFORM)  += xilinx-zynqmp.o
> > > > +obj-$(CONFIG_MPSOC_PLATFORM)  += xilinx-zynqmp-eemi.o
> > > > diff --git a/xen/arch/arm/platforms/xilinx-zynqmp-eemi.c
> > > > b/xen/arch/arm/platforms/xilinx-zynqmp-eemi.c
> > > > new file mode 100644
> > > > index 0000000..369bb3f
> > > > --- /dev/null
> > > > +++ b/xen/arch/arm/platforms/xilinx-zynqmp-eemi.c
> > > > @@ -0,0 +1,34 @@
> > > > +/*
> > > > + * xen/arch/arm/platforms/xilinx-zynqmp-eemi.c
> > > > + *
> > > > + * Xilinx ZynqMP EEMI API
> > > > + *
> > > > + * Copyright (c) 2018 Xilinx Inc.
> > > > + * Written by Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> > > > + *
> > > > + * This program is free software; you can redistribute it and/or
> > > > + * modify it under the terms and conditions of the GNU General Public
> > > > + * License, version 2, as published by the Free Software Foundation.
> > > > + *
> > > > + * This program is distributed in the hope that it will be useful,
> > > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > > > + * GNU General Public License for more details.
> > > > + */
> > > > +
> > > > +#include <asm/regs.h>
> > > > +#include <asm/platforms/xilinx-zynqmp-eemi.h>
> > > > +
> > > > +bool zynqmp_eemi(struct cpu_user_regs *regs)
> > > > +{
> > > > +    return false;
> > > > +}
> > > > +
> > > > +/*
> > > > + * Local variables:
> > > > + * mode: C
> > > > + * c-file-style: "BSD"
> > > > + * c-basic-offset: 4
> > > > + * indent-tabs-mode: nil
> > > > + * End:
> > > > + */
> > > > diff --git a/xen/arch/arm/platforms/xilinx-zynqmp.c
> > > > b/xen/arch/arm/platforms/xilinx-zynqmp.c
> > > > index d8ceded..9c174d2 100644
> > > > --- a/xen/arch/arm/platforms/xilinx-zynqmp.c
> > > > +++ b/xen/arch/arm/platforms/xilinx-zynqmp.c
> > > > @@ -18,6 +18,8 @@
> > > >     */
> > > >      #include <asm/platform.h>
> > > > +#include <asm/platforms/xilinx-zynqmp-eemi.h>
> > > > +#include <asm/smccc.h>
> > > >      static const char * const zynqmp_dt_compat[] __initconst =
> > > >    {
> > > > @@ -32,8 +34,17 @@ static const struct dt_device_match
> > > > zynqmp_blacklist_dev[] __initconst =
> > > >        { /* sentinel */ },
> > > >    };
> > > >    +static bool zynqmp_smc(struct cpu_user_regs *regs)
> > > > +{
> > > > +    if ( !is_64bit_domain(current->domain) )
> > > 
> > > Please document why you only expose eemi to 64-bit domain. What if the
> > > user
> > > start with 32-bit Dom0?
> > 
> > I'll add a in-code comment saying that only 64-bit guests are supported
> > by the current implementation -- the 32 bit EEMI ABI is not yet covered.
> 
> 64-bit guests is allowed to use both SMC32 and SMC64. There are actually some
> call that can only be done using SMC32 convention (see patch #6). So why
> forbid 32-bit domain when you allow 64-bit using SMC32?

I understand. It really looks like this check is a mistake. In fact, it
doesn't matter if a domain is 32bit or 64bit, the only thing that
matters for this code is if the EEMI calls are SMC32 and SMC64. So
instead of is_64bit_domain, I should check that SMC64 is used. Right?

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