Re: [RFC PATCH 3/7] MdeModulePkg/Dxe/Page: take MAX_ALLOC_ADDRESS into account

["Gao, Liming" <liming.gao@intel.com>]

Keep the same value of MAX_ADDRESS. There is no change now. 

Thanks
Liming
> -----Original Message-----
> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> Sent: Monday, December 10, 2018 10:54 PM
> To: Gao, Liming <liming.gao@intel.com>
> Cc: Wang, Jian J <jian.j.wang@intel.com>; Andrew Jones <drjones@redhat.com>; Wu, Hao A <hao.a.wu@intel.com>;
> edk2-devel@lists.01.org; Kinney, Michael D <michael.d.kinney@intel.com>; Laszlo Ersek <lersek@redhat.com>
> Subject: Re: [edk2] [RFC PATCH 3/7] MdeModulePkg/Dxe/Page: take MAX_ALLOC_ADDRESS into account
> 
> On Mon, 10 Dec 2018 at 15:52, Gao, Liming <liming.gao@intel.com> wrote:
> >
> > Ard:
> >   I prefer to define MAX_ALLOC_ADDRESS together with MAX_ADDRESS in ProcessorBind.h. I don't want to leave the choice to
> override MAX_ALLOC_ADDRESS definition.
> >
> 
> Seems reasonable. What should be the value for X64?
> 
> > Thanks
> > Liming
> > > -----Original Message-----
> > > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Ard Biesheuvel
> > > Sent: Monday, December 10, 2018 3:23 PM
> > > To: Wang, Jian J <jian.j.wang@intel.com>
> > > Cc: Andrew Jones <drjones@redhat.com>; Wu, Hao A <hao.a.wu@intel.com>; edk2-devel@lists.01.org; Gao, Liming
> > > <liming.gao@intel.com>; Kinney, Michael D <michael.d.kinney@intel.com>; Laszlo Ersek <lersek@redhat.com>
> > > Subject: Re: [edk2] [RFC PATCH 3/7] MdeModulePkg/Dxe/Page: take MAX_ALLOC_ADDRESS into account
> > >
> > > On Mon, 10 Dec 2018 at 03:04, Wang, Jian J <jian.j.wang@intel.com> wrote:
> > > >
> > > > Hi Ard,
> > > >
> > > > I think MAX_ALLOC_ADDRESS will affect other archs besides ARM. Please do enough
> > > > test for them (IA32/X64 for my concern).
> > > >
> > >
> > > For all other architectures, MAX_ADDRESS == MAX_ALLOC_ADDRESS is
> > > always true, so these changes only affect AARCH64.
> > >
> > > > In addition, do you think it's safer to replace MAX_ADDRESS with MAX_ALLOC_ADDRESS
> > > > in MemoryAllocationLib like following situation?
> > > >
> > > > (MdeModulePkg\Library\DxeCoreMemoryAllocationLib\MemoryAllocationLib.c)
> > > > VOID *
> > > > InternalAllocateCopyPool (
> > > >   IN EFI_MEMORY_TYPE  PoolType,
> > > >   IN UINTN            AllocationSize,
> > > >   IN CONST VOID       *Buffer
> > > >   )
> > > > {
> > > >   VOID  *Memory;
> > > >
> > > >   ASSERT (Buffer != NULL);
> > > >   ASSERT (AllocationSize <= (MAX_ADDRESS - (UINTN) Buffer + 1));
> > > >   ...
> > >
> > > This assert ensures that the copied buffer does not extend across the
> > > end of the address space and wraps. This is a separate concern, and is
> > > similar to numerous other occurrences of MAX_ADDRESS that maybe we
> > > should update as well at some point. However, it does not affect page
> > > allocation at all, it only puts an upper bound on the *size* of the
> > > allocation. So the changes as they are will be sufficient to ensure
> > > that AllocateCopyPool() does not allocate from a region that is not
> > > addressable by the CPU.
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