Re: [PATCH 1/2] EmbeddedPkg/NonCoherentDmaLib: implement support for DMA range limits

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

On Mon, Nov 25, 2019 at 13:52:24 +0100, Ard Biesheuvel wrote:
> > > -  if (MemoryType == EfiBootServicesData) {
> > > -    Allocation = AllocateAlignedPages (Pages, Alignment);
> > > -  } else if (MemoryType == EfiRuntimeServicesData) {
> > > -    Allocation = AllocateAlignedRuntimePages (Pages, Alignment);
> > > +  if (MemoryType == EfiBootServicesData ||
> > > +      MemoryType == EfiRuntimeServicesData) {
> > > +    Allocation = InternalAllocateAlignedPages (MemoryType, Pages, Alignment);
> > >    } else {
> > >      return EFI_INVALID_PARAMETER;
> > >    }
> > > @@ -479,6 +596,15 @@ NonCoherentDmaLibConstructor (
> > >  {
> > >    InitializeListHead (&UncachedAllocationList);
> > >
> > > +  //
> > > +  // Ensure that the combination of DMA addressing offset and limit produces
> > > +  // a sane value.
> > > +  //
> > > +  ASSERT (PcdGet64 (PcdDmaDeviceLimit) > PcdGet64 (PcdDmaDeviceOffset));
> >
> > Is this worth turning into a hard conditional and error return rather
> > than an assert? The following statement will end up wrapping downwards
> > if this condition is not true.
>
> 
> Constructor return values are only used in ASSERT_EFI_ERROR() calls in
> the ProcessLibraryConstructorList() routine that gets generated by the
> build tools (in AutoGen.c), so returning an error here would
> essentially be dead code, given that we would only make it to this
> point on builds that are known to ignore it.

Hmm, ack.
Print error message?

/
    Leif

> > > +
> > > +  mDmaHostAddressLimit = PcdGet64 (PcdDmaDeviceLimit) -
> > > +                         PcdGet64 (PcdDmaDeviceOffset);
> > > +
> >
> > /
> >     Leif
> >
> > >    // Get the Cpu protocol for later use
> > >    return gBS->LocateProtocol (&gEfiCpuArchProtocolGuid, NULL, (VOID **)&mCpu);
> > >  }
> > > diff --git a/EmbeddedPkg/Library/NonCoherentDmaLib/NonCoherentDmaLib.inf b/EmbeddedPkg/Library/NonCoherentDmaLib/NonCoherentDmaLib.inf
> > > index 2db751afee91..1a21cfe4ff23 100644
> > > --- a/EmbeddedPkg/Library/NonCoherentDmaLib/NonCoherentDmaLib.inf
> > > +++ b/EmbeddedPkg/Library/NonCoherentDmaLib/NonCoherentDmaLib.inf
> > > @@ -38,6 +38,7 @@ [Protocols]
> > >
> > >  [Pcd]
> > >    gEmbeddedTokenSpaceGuid.PcdDmaDeviceOffset
> > > +  gEmbeddedTokenSpaceGuid.PcdDmaDeviceLimit
> > >
> > >  [Depex]
> > >    gEfiCpuArchProtocolGuid
> > > --
> > > 2.17.1
> > >