On Tue, 27 Nov 2018 at 09:50, Sughosh Ganu <[email protected]> wrote:
>
> On Tue Nov 27, 2018 at 09:38:24AM +0100, Ard Biesheuvel wrote:
> > On Tue, 27 Nov 2018 at 09:36, Sughosh Ganu <[email protected]> wrote:
> > >
> > > 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 <[email protected]> wrote:
> > > > >
> > > > > From: Achin Gupta <[email protected]>
> > > > >
> > > > > 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 <[email protected]>
> > > > > ---
> > > > >  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.
> > >
> >
> > I'd strongly prefer this code to be generic if you are not using any
> > AArch64 specific facilities.
> >
> > AFAICT, we'd simply need to move the file out of the AArch64 directory
> > and rename [Sources.AARCH64] to [Sources] in the .inf file if the
> > header dependency is indeed superfluous.
>
> There are a couple of places where we use something like
> ARM_SVC_ID_SP_GET_MEM_ATTRIBUTES_AARCH64. Apart from this, it is
> generic.
>

And how do these deviate from their AArch32 counterparts?

I agree that ARM support is not essential right now, or perhaps never.
But I would like to understand the differences before I sign off on
this.

Thanks,
Ard.
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