Re: [PATCH] ArmPkg/ArmMmuLib: Add new attribute WRITE_BACK_NONSHAREABLE

[Leif Lindholm <leif.lindholm@linaro.org>]

On Tue, Nov 07, 2017 at 01:22:19PM +0000, Ard Biesheuvel wrote:
> On 7 November 2017 at 12:56, Heyi Guo <heyi.guo@linaro.org> wrote:
> > From: Peicong Li <lipeicong@huawei.com>
> >
> > Flash region needs to be set as cacheable (write back) to increase
> > performance, if PEI is still XIP on flash or DXE FV is decompressed
> > from flash FV. However some ARM platforms do not support to set flash
> > as inner shareable since flash is not normal DDR memory and it will
> > not respond to cache snoop request, which will causes system hang
> > after MMU is enabled.
> >
> > So we need a new ARM memory region attribute WRITE_BACK_NONSHAREABLE
> > for flash region on these platforms specifically. This attribute will
> > set the region as write back but not inner shared.
> >
> > Contributed-under: TianoCore Contribution Agreement 1.1
> > Signed-off-by: Peicong Li <lipeicong@huawei.com>
> > Signed-off-by: Heyi Guo <heyi.guo@linaro.org>
> > Cc: Leif Lindholm <leif.lindholm@linaro.org>
> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> 
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

> > ---
> >  ArmPkg/Include/Library/ArmLib.h                  | 7 +++++++
> >  ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c | 4 ++++
> >  2 files changed, 11 insertions(+)
> >
> > diff --git a/ArmPkg/Include/Library/ArmLib.h b/ArmPkg/Include/Library/ArmLib.h
> > index 24ffe9f..38199be 100644
> > --- a/ArmPkg/Include/Library/ArmLib.h
> > +++ b/ArmPkg/Include/Library/ArmLib.h
> > @@ -41,6 +41,13 @@ typedef enum {
> >    ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_UNCACHED_UNBUFFERED,
> >    ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK,
> >    ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_WRITE_BACK,
> > +  // On some platforms, memory mapped flash region is designed as not supporting
> > +  // shareable attribute, so WRITE_BACK_NONSHAREABLE is added for such special
> > +  // need.
> > +  // Do NOT use below two attributes if you are not sure.
> > +  ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK_NONSHAREABLE,
> > +  ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_WRITE_BACK_NONSHAREABLE,
> > +
> >    ARM_MEMORY_REGION_ATTRIBUTE_WRITE_THROUGH,
> >    ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_WRITE_THROUGH,
> >    ARM_MEMORY_REGION_ATTRIBUTE_DEVICE,
> > diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
> > index 8bd1c6f..4b62ecb 100644
> > --- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
> > +++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
> > @@ -35,6 +35,10 @@ ArmMemoryAttributeToPageAttribute (
> >    )
> >  {
> >    switch (Attributes) {
> > +  case ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK_NONSHAREABLE:
> > +  case ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_WRITE_BACK_NONSHAREABLE:
> > +    return TT_ATTR_INDX_MEMORY_WRITE_BACK;
> > +
> >    case ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK:
> >    case ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_WRITE_BACK:
> >      return TT_ATTR_INDX_MEMORY_WRITE_BACK | TT_SH_INNER_SHAREABLE;
> > --
> > 2.7.2.windows.1
> >