Re: [Patch V6 04/22] UefiCpuPkg/CpuPageTableLib: Fix the non-1:1 mapping issue

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

Reviewed-by: Ray Ni <ray.ni@intel.com>

> -----Original Message-----
> From: Tan, Dun <dun.tan@intel.com>
> Sent: Friday, March 24, 2023 4:52 PM
> To: devel@edk2.groups.io
> Cc: Dong, Eric <eric.dong@intel.com>; Ni, Ray <ray.ni@intel.com>; Kumar,
> Rahul R <rahul.r.kumar@intel.com>; Gerd Hoffmann <kraxel@redhat.com>
> Subject: [Patch V6 04/22] UefiCpuPkg/CpuPageTableLib: Fix the non-1:1
> mapping issue
> 
> In previous code logic, when splitting a leaf parent entry to
> smaller granularity child page table, if the parent entry
> Attribute&Mask(without PageTableBaseAddress field) is equal to the
> input attribute&mask(without PageTableBaseAddress field), the split
> process won't happen. This may lead to failure in non-1:1 mapping.
> 
> For example, there is a page table in which [0, 1G] is mapped(Lv4[0]
> ,Lv3[0,0], a non-leaf level4 entry and a leaf level3 entry). And we
> want to remap [0, 2M] linear address range to [1G, 1G + 2M] with the
> same attibute. The expected behaviour should be: split Lv3[0,0]
> entry into 512 level2 entries and remap the first level2 entry to
> cover [0, 2M]. But the split won't happen in previous code since
> PageTableBaseAddress of input Attribute is not checked.
> 
> So, when checking if a leaf parent entry needs to be splitted, we
> should also check if PageTableBaseAddress calculated by parent entry
> is equal to the value caculated by input attribute.
> 
> Signed-off-by: Dun Tan <dun.tan@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Tested-by: Gerd Hoffmann <kraxel@redhat.com>
> Acked-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c | 12
> +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> index 127b65183f..b94ef07c56 100644
> --- a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> +++ b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> @@ -274,6 +274,8 @@ PageTableLibMapInLevel (
>    IA32_MAP_ATTRIBUTE  ChildMask;
>    IA32_MAP_ATTRIBUTE  CurrentMask;
>    IA32_MAP_ATTRIBUTE  LocalParentAttribute;
> +  UINT64              PhysicalAddrInEntry;
> +  UINT64              PhysicalAddrInAttr;
> 
>    ASSERT (Level != 0);
>    ASSERT ((Attribute != NULL) && (Mask != NULL));
> @@ -341,7 +343,15 @@ PageTableLibMapInLevel (
>        // This function is called when the memory length is less than the region
> length of the parent level.
>        // No need to split the page when the attributes equal.
>        //
> -      return RETURN_SUCCESS;
> +      if (Mask->Bits.PageTableBaseAddress == 0) {
> +        return RETURN_SUCCESS;
> +      }
> +
> +      PhysicalAddrInEntry =
> IA32_MAP_ATTRIBUTE_PAGE_TABLE_BASE_ADDRESS (&PleBAttribute) +
> MultU64x32 (RegionLength, (UINT32)PagingEntryIndex);
> +      PhysicalAddrInAttr  =
> (IA32_MAP_ATTRIBUTE_PAGE_TABLE_BASE_ADDRESS (Attribute) + Offset)
> & (~RegionMask);
> +      if (PhysicalAddrInEntry == PhysicalAddrInAttr) {
> +        return RETURN_SUCCESS;
> +      }
>      }
> 
>      ASSERT (Buffer == NULL || *BufferSize >= SIZE_4KB);
> --
> 2.31.1.windows.1