1 /** @file
2
3 AMD Sev Dxe driver. This driver is dispatched early in DXE, due to being list
4 in APRIORI. It clears C-bit from MMIO and NonExistent Memory space when SEV
5 is enabled.
6
7 Copyright (c) 2017, AMD Inc. All rights reserved.<BR>
8
9 SPDX-License-Identifier: BSD-2-Clause-Patent
10
11 **/
12
13 #include <Library/BaseLib.h>
14 #include <Library/BaseMemoryLib.h>
15 #include <Library/DebugLib.h>
16 #include <Library/DxeServicesTableLib.h>
17 #include <Library/MemEncryptSevLib.h>
18 #include <Library/MemoryAllocationLib.h>
19 #include <Library/PcdLib.h>
20
21 EFI_STATUS
22 EFIAPI
AmdSevDxeEntryPoint(IN EFI_HANDLE ImageHandle,IN EFI_SYSTEM_TABLE * SystemTable)23 AmdSevDxeEntryPoint (
24 IN EFI_HANDLE ImageHandle,
25 IN EFI_SYSTEM_TABLE *SystemTable
26 )
27 {
28 EFI_STATUS Status;
29 EFI_GCD_MEMORY_SPACE_DESCRIPTOR *AllDescMap;
30 UINTN NumEntries;
31 UINTN Index;
32
33 //
34 // Do nothing when SEV is not enabled
35 //
36 if (!MemEncryptSevIsEnabled ()) {
37 return EFI_UNSUPPORTED;
38 }
39
40 //
41 // Iterate through the GCD map and clear the C-bit from MMIO and NonExistent
42 // memory space. The NonExistent memory space will be used for mapping the
43 // MMIO space added later (eg PciRootBridge). By clearing both known MMIO and
44 // NonExistent memory space can gurantee that current and furture MMIO adds
45 // will have C-bit cleared.
46 //
47 Status = gDS->GetMemorySpaceMap (&NumEntries, &AllDescMap);
48 if (!EFI_ERROR (Status)) {
49 for (Index = 0; Index < NumEntries; Index++) {
50 CONST EFI_GCD_MEMORY_SPACE_DESCRIPTOR *Desc;
51
52 Desc = &AllDescMap[Index];
53 if (Desc->GcdMemoryType == EfiGcdMemoryTypeMemoryMappedIo ||
54 Desc->GcdMemoryType == EfiGcdMemoryTypeNonExistent) {
55 Status = MemEncryptSevClearPageEncMask (
56 0,
57 Desc->BaseAddress,
58 EFI_SIZE_TO_PAGES (Desc->Length),
59 FALSE
60 );
61 ASSERT_EFI_ERROR (Status);
62 }
63 }
64
65 FreePool (AllDescMap);
66 }
67
68 //
69 // When SMM is enabled, clear the C-bit from SMM Saved State Area
70 //
71 // NOTES: The SavedStateArea address cleared here is before SMBASE
72 // relocation. Currently, we do not clear the SavedStateArea address after
73 // SMBASE is relocated due to the following reasons:
74 //
75 // 1) Guest BIOS never access the relocated SavedStateArea.
76 //
77 // 2) The C-bit works on page-aligned address, but the SavedStateArea
78 // address is not a page-aligned. Theoretically, we could roundup the address
79 // and clear the C-bit of aligned address but looking carefully we found
80 // that some portion of the page contains code -- which will causes a bigger
81 // issues for SEV guest. When SEV is enabled, all the code must be encrypted
82 // otherwise hardware will cause trap.
83 //
84 // We restore the C-bit for this SMM Saved State Area after SMBASE relocation
85 // is completed (See OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c).
86 //
87 if (FeaturePcdGet (PcdSmmSmramRequire)) {
88 UINTN MapPagesBase;
89 UINTN MapPagesCount;
90
91 Status = MemEncryptSevLocateInitialSmramSaveStateMapPages (
92 &MapPagesBase,
93 &MapPagesCount
94 );
95 ASSERT_EFI_ERROR (Status);
96
97 //
98 // Although these pages were set aside (i.e., allocated) by PlatformPei, we
99 // could be after a warm reboot from the OS. Don't leak any stale OS data
100 // to the hypervisor.
101 //
102 ZeroMem ((VOID *)MapPagesBase, EFI_PAGES_TO_SIZE (MapPagesCount));
103
104 Status = MemEncryptSevClearPageEncMask (
105 0, // Cr3BaseAddress -- use current CR3
106 MapPagesBase, // BaseAddress
107 MapPagesCount, // NumPages
108 TRUE // Flush
109 );
110 if (EFI_ERROR (Status)) {
111 DEBUG ((DEBUG_ERROR, "%a: MemEncryptSevClearPageEncMask(): %r\n",
112 __FUNCTION__, Status));
113 ASSERT (FALSE);
114 CpuDeadLoop ();
115 }
116 }
117
118 return EFI_SUCCESS;
119 }
120