[edk2-devel] [PATCH 2/4] UefiCpuPkg/CpuDxe: Support parsing 5-level page table
Laszlo Ersek
lersek at redhat.com
Tue Jul 23 09:22:36 UTC 2019
On 07/22/19 10:15, Ni, Ray wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2008
>
> Signed-off-by: Ray Ni <ray.ni at intel.com>
> Cc: Eric Dong <eric.dong at intel.com>
> Cc: Laszlo Ersek <lersek at redhat.com>
> ---
> UefiCpuPkg/CpuDxe/CpuPageTable.c | 22 ++++++++++++++++++++--
> 1 file changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/UefiCpuPkg/CpuDxe/CpuPageTable.c b/UefiCpuPkg/CpuDxe/CpuPageTable.c
> index c369b44f12..8e959eb2b7 100644
> --- a/UefiCpuPkg/CpuDxe/CpuPageTable.c
> +++ b/UefiCpuPkg/CpuDxe/CpuPageTable.c
> @@ -1,7 +1,7 @@
> /** @file
> Page table management support.
>
> - Copyright (c) 2017, Intel Corporation. All rights reserved.<BR>
> + Copyright (c) 2017 - 2019, Intel Corporation. All rights reserved.<BR>
> Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
>
> SPDX-License-Identifier: BSD-2-Clause-Patent
> @@ -276,25 +276,43 @@ GetPageTableEntry (
> UINTN Index2;
> UINTN Index3;
> UINTN Index4;
> + UINTN Index5;
> UINT64 *L1PageTable;
> UINT64 *L2PageTable;
> UINT64 *L3PageTable;
> UINT64 *L4PageTable;
> + UINT64 *L5PageTable;
> UINT64 AddressEncMask;
> + IA32_CR4 Cr4;
> + BOOLEAN Enable5LevelPaging;
>
> ASSERT (PagingContext != NULL);
>
> + Index5 = ((UINTN)RShiftU64 (Address, 48)) & PAGING_PAE_INDEX_MASK;
> Index4 = ((UINTN)RShiftU64 (Address, 39)) & PAGING_PAE_INDEX_MASK;
> Index3 = ((UINTN)Address >> 30) & PAGING_PAE_INDEX_MASK;
> Index2 = ((UINTN)Address >> 21) & PAGING_PAE_INDEX_MASK;
> Index1 = ((UINTN)Address >> 12) & PAGING_PAE_INDEX_MASK;
>
> + Cr4.UintN = AsmReadCr4 ();
> + Enable5LevelPaging = (BOOLEAN) (Cr4.Bits.LA57 == 1);
> +
> // Make sure AddressEncMask is contained to smallest supported address field.
> //
> AddressEncMask = PcdGet64 (PcdPteMemoryEncryptionAddressOrMask) & PAGING_1G_ADDRESS_MASK_64;
>
> if (PagingContext->MachineType == IMAGE_FILE_MACHINE_X64) {
> - L4PageTable = (UINT64 *)(UINTN)PagingContext->ContextData.X64.PageTableBase;
> + if (Enable5LevelPaging) {
> + L5PageTable = (UINT64 *)(UINTN)PagingContext->ContextData.X64.PageTableBase;
> + if (L5PageTable[Index5] == 0) {
> + *PageAttribute = PageNone;
> + return NULL;
> + }
> +
> + L4PageTable = (UINT64 *)(UINTN)(L5PageTable[Index5] & ~AddressEncMask & PAGING_4K_ADDRESS_MASK_64);
> + } else {
> + L4PageTable = (UINT64 *)(UINTN)PagingContext->ContextData.X64.PageTableBase;
> + }
> if (L4PageTable[Index4] == 0) {
> *PageAttribute = PageNone;
> return NULL;
>
The patch seems to be a no-op if Enable5LevelPaging is FALSE, so that's
good.
Questions:
(1) Same question as under patch #1: is the CR4 check reliable on AMD
processors too?
(2) Should we read CR4 (or call CPUID) every time this function is
invoked? Can we perform the check at CpuDxe startup, and cache the result?
(3) Should we consider the PCD (from patch #3) before accessing the
hardware (CR4 / CPUID alike)?
Thanks
Laszlo
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