Re: [PATCH v4 5/5] ArmPkg/ArmMmuLib: Add MMU Library suitable for use in S-EL0.

[Sughosh Ganu <sughosh.ganu@arm.com>]

hi Ard,

On Tue Nov 27, 2018 at 09:14:52AM +0100, Ard Biesheuvel wrote:
> On Tue, 27 Nov 2018 at 07:20, Sughosh Ganu <sughosh.ganu@arm.com> wrote:
> >
> > From: Achin Gupta <achin.gupta@arm.com>
> >
> > The Standalone MM environment runs in S-EL0 in AArch64 on ARM Standard
> > Platforms. Privileged firmware e.g. ARM Trusted Firmware sets up its
> > architectural context including the initial translation tables for the
> > S-EL1/EL0 translation regime. The MM environment will still request ARM
> > TF to change the memory attributes of memory regions during
> > initialization.
> >
> > The Standalone MM image is a FV that encapsulates the MM foundation
> > and drivers. These are PE-COFF images with data and text segments.
> > To initialise the MM environment, Arm Trusted Firmware has to create
> > translation tables with sane default attributes for the memory
> > occupied by the FV. This library sends SVCs to ARM Trusted Firmware
> > to request memory permissions change for data and text segments.
> >
> > This patch adds a simple MMU library suitable for execution in S-EL0 and
> > requesting memory permissions change operations from Arm Trusted Firmware.
> >
> > Contributed-under: TianoCore Contribution Agreement 1.1
> > Signed-off-by: Sughosh Ganu <sughosh.ganu@arm.com>
> > ---
> >  ArmPkg/ArmPkg.dec                                                                                                                                       |   1 +
> >  ArmVirtPkg/Library/XenArmGenericTimerVirtCounterLib/XenArmGenericTimerVirtCounterLib.inf => ArmPkg/Library/StandaloneMmMmuLib/ArmMmuStandaloneMmLib.inf |  23 +--
> >  ArmPkg/Include/Library/{ArmMmuLib.h => StandaloneMmMmuLib.h}                                                                                            |  38 +---
> >  ArmPkg/Library/StandaloneMmMmuLib/Aarch64/ArmMmuStandaloneMmLib.c                                                                                       | 185 ++++++++++++++++++++
> >  4 files changed, 203 insertions(+), 44 deletions(-)


<snip>

> > +#endif /* __STANDALONEMM_MMU_LIB__ */
> > diff --git a/ArmPkg/Library/StandaloneMmMmuLib/Aarch64/ArmMmuStandaloneMmLib.c b/ArmPkg/Library/StandaloneMmMmuLib/Aarch64/ArmMmuStandaloneMmLib.c
> > new file mode 100644
> > index 000000000000..d7d87b7d5d69
> > --- /dev/null
> > +++ b/ArmPkg/Library/StandaloneMmMmuLib/Aarch64/ArmMmuStandaloneMmLib.c
> > @@ -0,0 +1,185 @@
> > +/** @file
> > +*  File managing the MMU for ARMv8 architecture in S-EL0
> > +*
> > +*  Copyright (c) 2017 - 2018, ARM Limited. All rights reserved.
> > +*
> > +*  This program and the accompanying materials
> > +*  are licensed and made available under the terms and conditions of the BSD License
> > +*  which accompanies this distribution.  The full text of the license may be found at
> > +*  http://opensource.org/licenses/bsd-license.php
> > +*
> > +*  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
> > +*  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> > +*
> > +**/
> > +
> > +#include <Uefi.h>
> > +#include <Chipset/AArch64.h>
> 
> Why do you need this include? If you can drop it, can you also make
> the library generic (i.e., supporting ARM as well as AArch64) ?
> 
> (apologies for not spotting this before)

I can remove the header file if it is superfluous. But regarding your
comment on making this code generic for Arm as well, i guess we
can work on refactoring the code when/if we actually require to
support this on Arm. I am not sure if we are going to have a use-case
for StandaloneMM on Arm. Currently, we are only supporting it on
Aarch64 based platforms. Is that fine. Please let me know. Thanks.

-sughosh