[edk2-devel] [Patch] StandaloneMmPkg: Fixed communicating from TF-A failed issue

[Omkar Anand Kulkarni]

On 6/10/21 6:44 AM, Ming Huang via groups.io wrote:
> On 6/9/21 3:10 PM, Ard Biesheuvel wrote:
> > On Tue, 8 Jun 2021 at 16:21, Ming Huang <huangming at linux.alibaba.com>
> wrote:
> >>
> >> TF-A: TrustedFirmware-a
> >> SPM: Secure Partition Manager(MM)
> >>
> >> For AArch64, when SPM enable in TF-A, TF-A may communicate to MM
> with
> >> buffer address (PLAT_SPM_BUF_BASE). The address is different from
> >> PcdMmBufferBase which use in edk2.
> >
> > Then why do we have PcdMmBufferBase?
> 
> ArmPkg use this Pcd for the base address of non-secure communication
> buffer.
> 
> >
> > Is it possible to set PcdMmBufferBase to the correct value?
> 
> The secure communication may interrupt the non-secure communication. if
> we use the same address (PcdMmBufferBase and PLAT_SPM_BUF_BASE), the
> date in communication buffer may be corrupted.
> 
> Best Regards,
> Ming

In case where an interrupt handler executing from EL3 makes a call into StandaloneMM, the handler in EL3 makes an spm call into StandaloneMM using PLAT_SPM_BUF_BASE buffer base address. This PLAT_SPM_BUF_BASE is a shared buffer between EL3 and S-EL0. This is where the following check fails and leads to spm call failure. So this change would help resolve this issue.

- Omkar

> 
> >
> >> Checking address will let TF-A communicate failed to MM. So remove
> >> below checking code:
> >> if (NsCommBufferAddr < mNsCommBuffer.PhysicalStart) {
> >>   return EFI_ACCESS_DENIED;
> >> }
> >>
> >> Signed-off-by: Ming Huang <huangming at linux.alibaba.com>
> >> ---
> >>  StandaloneMmPkg/Drivers/StandaloneMmCpu/AArch64/EventHandle.c |
> 4
> >> ----
> >>  1 file changed, 4 deletions(-)
> >>
> >> diff --git
> >> a/StandaloneMmPkg/Drivers/StandaloneMmCpu/AArch64/EventHandle.c
> >> b/StandaloneMmPkg/Drivers/StandaloneMmCpu/AArch64/EventHandle.c
> >> index 63fbe26642..fe98d3181d 100644
> >> ---
> a/StandaloneMmPkg/Drivers/StandaloneMmCpu/AArch64/EventHandle.c
> >> +++
> b/StandaloneMmPkg/Drivers/StandaloneMmCpu/AArch64/EventHandle.c
> >> @@ -103,10 +103,6 @@ PiMmStandaloneArmTfCpuDriverEntry (
> >>      return EFI_INVALID_PARAMETER;
> >>    }
> >>
> >> -  if (NsCommBufferAddr < mNsCommBuffer.PhysicalStart) {
> >> -    return EFI_ACCESS_DENIED;
> >> -  }
> >> -
> >>    if ((NsCommBufferAddr + sizeof (EFI_MM_COMMUNICATE_HEADER)) >=
> >>        (mNsCommBuffer.PhysicalStart + mNsCommBuffer.PhysicalSize)) {
> >>      return EFI_INVALID_PARAMETER;
> >> --
> >> 2.17.1
> >>
> 
> 
> 
> 



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