Re: [edk2-devel] [PATCH v2 1/2] UefiCpuPkg: Add PCD PcdCpuSmmAccessOut to control SMM access out

["Ni, Ray" <ray.ni@intel.com>]

Laszlo,
I appreciate your Reviewed-by on the new PCD creation.

But let's continue discussing on the other mail thread:
[edk2-devel] [PATCH v2 2/2] UefiCpuPkg/PiSmmCpu: PcdCpuSmmAccessOut controls SMM access-out policy

Thanks,
Ray

> -----Original Message-----
> From: Laszlo Ersek <lersek@redhat.com>
> Sent: Thursday, August 1, 2019 6:22 AM
> To: devel@edk2.groups.io; Ni, Ray <ray.ni@intel.com>
> Cc: Dong, Eric <eric.dong@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>
> Subject: Re: [edk2-devel] [PATCH v2 1/2] UefiCpuPkg: Add PCD
> PcdCpuSmmAccessOut to control SMM access out
> 
> On 07/31/19 18:38, Ni, Ray wrote:
> > There is a requirement to allow SMM code access non-SMRAM memory
> after
> > ReadyToLock.
> > The requirement was expected to be satisfied by commit:
> > c60d36b4d1ee1f69b7cca897d3621dfa951895c2
> > * UefiCpuPkg/SmmCpu: Block access-out only when static paging is used
> >
> > Commit c60d36b4 re-interpreted the PcdCpuSmmStaticPageTable as a way
> > to control whether SMM module can access non-SMRAM memory after
> > ReadyToLock.
> > It brought confusion because "static page table" means the page table
> > is created in advance and there is no dynamic page table modification
> > at runtime. It only applies to 64bit environment because page table
> > for memory below 4GB is always created in advance. But the control of
> > whether allowing SMM module access non-SMRAM memory can also be
> > applied to 32bit environment.
> > It makes more sense to have a separate PCD as proposed in this patch
> > to control the policy.
> >
> > Signed-off-by: Ray Ni <ray.ni@intel.com>
> > Cc: Eric Dong <eric.dong@intel.com>
> > Cc: Laszlo Ersek <lersek@redhat.com>
> > Cc: Jiewen Yao <jiewen.yao@intel.com>
> > ---
> >  UefiCpuPkg/UefiCpuPkg.dec | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/UefiCpuPkg/UefiCpuPkg.dec b/UefiCpuPkg/UefiCpuPkg.dec
> > index 6ddf0cd224..24b44bae39 100644
> > --- a/UefiCpuPkg/UefiCpuPkg.dec
> > +++ b/UefiCpuPkg/UefiCpuPkg.dec
> > @@ -246,6 +246,13 @@ [PcdsFixedAtBuild, PcdsPatchableInModule,
> PcdsDynamic, PcdsDynamicEx]
> >    # @Prompt Use static page table for all memory in SMM.
> >
> >
> gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStaticPageTable|TRUE|BOOLEAN
> |0x3213
> > 210D
> >
> > +  ## Controls whether SMM modules can access all non-SMRAM memory
> after SmmReadyToLock.
> > +  #   TRUE  - SMM modules can access all non-SMRAM memory after
> SmmReadyToLock.<BR>
> > +  #   FALSE - SMM modules can only access reserved, runtime and ACPI
> NVS type of non-SMRAM memory
> > +  #           after SmmReadyToLock.<BR>
> > +  # @Prompt SMM modules can access all non-SMRAM memory after
> SmmReadyToLock.
> > +
> > +
> gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmAccessOut|FALSE|BOOLEAN|0x3
> 213210
> > + F
> > +
> >    ## Specifies timeout value in microseconds for the BSP in SMM to wait for
> all APs to come into SMM.
> >    # @Prompt AP synchronization timeout value in SMM.
> >
> >
> gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout|1000000|UINT64
> |0x3213
> > 2104
> >
> 
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>