[edk2-devel] [RFC PATCH 11/14] OvmfPkg/AmdSev: Build page table for migration handler
Dov Murik
dovmurik at linux.vnet.ibm.com
Wed Mar 3 18:58:43 UTC 2021
On 03/03/2021 18:32, Ashish Kalra wrote:
> On Tue, Mar 02, 2021 at 03:48:36PM -0500, Tobin Feldman-Fitzthum wrote:
>> From: Dov Murik <dovmurik at linux.ibm.com>
>>
>> The migration handler builds its own page tables and switches
>> to them. The MH pagetables are reserved as runtime memory.
>>
>> When the hypervisor asks the MH to import/export a page, the HV
>> writes the guest physical address of the page in question to the
>> mailbox. The MH uses an identity mapping so that it can read/write
>> whatever GPA is requested by the HV. The hypervisor only asks the
>> MH to import/export encrypted pages. Thus, the C-Bit can be set
>> for every page in the identity map.
>>
>> The MH also needs to read shared pages, such as the mailbox.
>> These are mapped at an offset. The offset must be added to
>> the physical address before it can be resolved.
>>
>> Signed-off-by: Tobin Feldman-Fitzthum <tobin at linux.ibm.com>
>> Signed-off-by: Dov Murik <dovmurik at linux.vnet.ibm.com>
>> ---
>> .../ConfidentialMigrationDxe.inf | 1 +
>> .../ConfidentialMigration/VirtualMemory.h | 177 ++++++++++++++++++
>> .../ConfidentialMigrationDxe.c | 88 ++++++++-
>> 3 files changed, 265 insertions(+), 1 deletion(-)
>> create mode 100644 OvmfPkg/AmdSev/ConfidentialMigration/VirtualMemory.h
>>
>> diff --git a/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.inf b/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.inf
>> index 49457d5d17..8dadfd1d13 100644
>> --- a/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.inf
>> +++ b/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.inf
>> @@ -15,6 +15,7 @@
>>
>> [Sources]
>> ConfidentialMigrationDxe.c
>> + VirtualMemory.h
>>
>> [Packages]
>> MdePkg/MdePkg.dec
>> diff --git a/OvmfPkg/AmdSev/ConfidentialMigration/VirtualMemory.h b/OvmfPkg/AmdSev/ConfidentialMigration/VirtualMemory.h
>> new file mode 100644
>> index 0000000000..c50cb64c63
>> --- /dev/null
>> +++ b/OvmfPkg/AmdSev/ConfidentialMigration/VirtualMemory.h
>> @@ -0,0 +1,177 @@
>> +/** @file
>> + Virtual Memory Management Services to set or clear the memory encryption bit
>> + Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
>> + Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
>> + SPDX-License-Identifier: BSD-2-Clause-Patent
>> + Code is derived from OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.h
>> +
>> +**/
>> +
>> +#ifndef __VIRTUAL_MEMORY__
>> +#define __VIRTUAL_MEMORY__
>> +
>> +#include <Library/BaseLib.h>
>> +#include <Library/BaseMemoryLib.h>
>> +#include <Library/CacheMaintenanceLib.h>
>> +#include <Library/DebugLib.h>
>> +#include <Library/MemoryAllocationLib.h>
>> +#include <Uefi.h>
>> +
>> +#define SYS_CODE64_SEL 0x38
>> +
>> +#pragma pack(1)
>> +
>> +//
>> +// Page-Map Level-4 Offset (PML4) and
>> +// Page-Directory-Pointer Offset (PDPE) entries 4K & 2MB
>> +//
>> +
>> +typedef union {
>> + struct {
>> + UINT64 Present:1; // 0 = Not present in memory,
>> + // 1 = Present in memory
>> + UINT64 ReadWrite:1; // 0 = Read-Only, 1= Read/Write
>> + UINT64 UserSupervisor:1; // 0 = Supervisor, 1=User
>> + UINT64 WriteThrough:1; // 0 = Write-Back caching,
>> + // 1 = Write-Through caching
>> + UINT64 CacheDisabled:1; // 0 = Cached, 1=Non-Cached
>> + UINT64 Accessed:1; // 0 = Not accessed,
>> + // 1 = Accessed (set by CPU)
>> + UINT64 Reserved:1; // Reserved
>> + UINT64 MustBeZero:2; // Must Be Zero
>> + UINT64 Available:3; // Available for use by system software
>> + UINT64 PageTableBaseAddress:40; // Page Table Base Address
>> + UINT64 AvabilableHigh:11; // Available for use by system software
>> + UINT64 Nx:1; // No Execute bit
>> + } Bits;
>> + UINT64 Uint64;
>> +} PAGE_MAP_AND_DIRECTORY_POINTER;
>> +
>> +//
>> +// Page Table Entry 4KB
>> +//
>> +typedef union {
>> + struct {
>> + UINT64 Present:1; // 0 = Not present in memory,
>> + // 1 = Present in memory
>> + UINT64 ReadWrite:1; // 0 = Read-Only, 1= Read/Write
>> + UINT64 UserSupervisor:1; // 0 = Supervisor, 1=User
>> + UINT64 WriteThrough:1; // 0 = Write-Back caching,
>> + // 1 = Write-Through caching
>> + UINT64 CacheDisabled:1; // 0 = Cached, 1=Non-Cached
>> + UINT64 Accessed:1; // 0 = Not accessed,
>> + // 1 = Accessed (set by CPU)
>> + UINT64 Dirty:1; // 0 = Not Dirty, 1 = written by
>> + // processor on access to page
>> + UINT64 PAT:1; //
>> + UINT64 Global:1; // 0 = Not global page, 1 = global page
>> + // TLB not cleared on CR3 write
>> + UINT64 Available:3; // Available for use by system software
>> + UINT64 PageTableBaseAddress:40; // Page Table Base Address
>> + UINT64 AvabilableHigh:11; // Available for use by system software
>> + UINT64 Nx:1; // 0 = Execute Code,
>> + // 1 = No Code Execution
>> + } Bits;
>> + UINT64 Uint64;
>> +} PAGE_TABLE_4K_ENTRY;
>> +
>> +//
>> +// Page Table Entry 2MB
>> +//
>> +typedef union {
>> + struct {
>> + UINT64 Present:1; // 0 = Not present in memory,
>> + // 1 = Present in memory
>> + UINT64 ReadWrite:1; // 0 = Read-Only, 1= Read/Write
>> + UINT64 UserSupervisor:1; // 0 = Supervisor, 1=User
>> + UINT64 WriteThrough:1; // 0 = Write-Back caching,
>> + // 1=Write-Through caching
>> + UINT64 CacheDisabled:1; // 0 = Cached, 1=Non-Cached
>> + UINT64 Accessed:1; // 0 = Not accessed,
>> + // 1 = Accessed (set by CPU)
>> + UINT64 Dirty:1; // 0 = Not Dirty, 1 = written by
>> + // processor on access to page
>> + UINT64 MustBe1:1; // Must be 1
>> + UINT64 Global:1; // 0 = Not global page, 1 = global page
>> + // TLB not cleared on CR3 write
>> + UINT64 Available:3; // Available for use by system software
>> + UINT64 PAT:1; //
>> + UINT64 MustBeZero:8; // Must be zero;
>> + UINT64 PageTableBaseAddress:31; // Page Table Base Address
>> + UINT64 AvabilableHigh:11; // Available for use by system software
>> + UINT64 Nx:1; // 0 = Execute Code,
>> + // 1 = No Code Execution
>> + } Bits;
>> + UINT64 Uint64;
>> +} PAGE_TABLE_ENTRY;
>> +
>> +//
>> +// Page Table Entry 1GB
>> +//
>> +typedef union {
>> + struct {
>> + UINT64 Present:1; // 0 = Not present in memory,
>> + // 1 = Present in memory
>> + UINT64 ReadWrite:1; // 0 = Read-Only, 1= Read/Write
>> + UINT64 UserSupervisor:1; // 0 = Supervisor, 1=User
>> + UINT64 WriteThrough:1; // 0 = Write-Back caching,
>> + // 1 = Write-Through caching
>> + UINT64 CacheDisabled:1; // 0 = Cached, 1=Non-Cached
>> + UINT64 Accessed:1; // 0 = Not accessed,
>> + // 1 = Accessed (set by CPU)
>> + UINT64 Dirty:1; // 0 = Not Dirty, 1 = written by
>> + // processor on access to page
>> + UINT64 MustBe1:1; // Must be 1
>> + UINT64 Global:1; // 0 = Not global page, 1 = global page
>> + // TLB not cleared on CR3 write
>> + UINT64 Available:3; // Available for use by system software
>> + UINT64 PAT:1; //
>> + UINT64 MustBeZero:17; // Must be zero;
>> + UINT64 PageTableBaseAddress:22; // Page Table Base Address
>> + UINT64 AvabilableHigh:11; // Available for use by system software
>> + UINT64 Nx:1; // 0 = Execute Code,
>> + // 1 = No Code Execution
>> + } Bits;
>> + UINT64 Uint64;
>> +} PAGE_TABLE_1G_ENTRY;
>> +
>> +#pragma pack()
>> +
>> +#define IA32_PG_P BIT0
>> +#define IA32_PG_RW BIT1
>> +#define IA32_PG_PS BIT7
>> +
>> +#define PAGING_PAE_INDEX_MASK 0x1FF
>> +
>> +#define PAGING_4K_ADDRESS_MASK_64 0x000FFFFFFFFFF000ull
>> +#define PAGING_2M_ADDRESS_MASK_64 0x000FFFFFFFE00000ull
>> +#define PAGING_1G_ADDRESS_MASK_64 0x000FFFFFC0000000ull
>> +
>> +#define PAGING_L1_ADDRESS_SHIFT 12
>> +#define PAGING_L2_ADDRESS_SHIFT 21
>> +#define PAGING_L3_ADDRESS_SHIFT 30
>> +#define PAGING_L4_ADDRESS_SHIFT 39
>> +
>> +#define PAGING_PML4E_NUMBER 4
>> +
>> +#define PAGETABLE_ENTRY_MASK ((1UL << 9) - 1)
>> +#define PML4_OFFSET(x) ( (x >> 39) & PAGETABLE_ENTRY_MASK)
>> +#define PDP_OFFSET(x) ( (x >> 30) & PAGETABLE_ENTRY_MASK)
>> +#define PDE_OFFSET(x) ( (x >> 21) & PAGETABLE_ENTRY_MASK)
>> +#define PTE_OFFSET(x) ( (x >> 12) & PAGETABLE_ENTRY_MASK)
>> +#define PAGING_1G_ADDRESS_MASK_64 0x000FFFFFC0000000ull
>> +
>> +#define PAGE_TABLE_POOL_ALIGNMENT BASE_2MB
>> +#define PAGE_TABLE_POOL_UNIT_SIZE SIZE_2MB
>> +#define PAGE_TABLE_POOL_UNIT_PAGES \
>> + EFI_SIZE_TO_PAGES (PAGE_TABLE_POOL_UNIT_SIZE)
>> +#define PAGE_TABLE_POOL_ALIGN_MASK \
>> + (~(EFI_PHYSICAL_ADDRESS)(PAGE_TABLE_POOL_ALIGNMENT - 1))
>> +
>> +typedef struct {
>> + VOID *NextPool;
>> + UINTN Offset;
>> + UINTN FreePages;
>> +} PAGE_TABLE_POOL;
>> +
>> +#endif
>> diff --git a/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.c b/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.c
>> index 8402fcc4fa..3df3b09732 100644
>> --- a/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.c
>> +++ b/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.c
>> @@ -11,6 +11,7 @@
>> #include <Protocol/MpService.h>
>> #include <Library/BaseMemoryLib.h>
>>
>> +#include "VirtualMemory.h"
>> //
>> // Functions implemented by the migration handler
>> //
>> @@ -43,6 +44,83 @@ typedef volatile struct {
>> UINT32 done;
>> } MH_COMMAND_PARAMETERS;
>>
>> +//
>> +// Addresses for MH page table.
>> +//
>> +STATIC PAGE_TABLE_POOL *mPageTablePool = NULL;
>> +STATIC PHYSICAL_ADDRESS mMigrationHelperPageTables = 0;
>> +
>> +//
>> +// Offset for non-cbit mapping.
>> +//
>> +#define UNENC_VIRT_ADDR_BASE 0xffffff8000000000ULL
>> +
>> +
>> +/**
>> + Allocates and fills in custom page tables for Migration Handler.
>> + The MH must be able to write to any encrypted page. Thus, it
>> + uses an identity map where the C-bit is set for every page. The
>> + HV should never ask the MH to import/export a shared page. The
>> + MH must also be able to read some shared pages. The first 1GB
>> + of memory is mapped at offset UNENC_VIRT_ADDR_BASE.
>> +
>> +**/
>> +VOID
>> +PrepareMigrationHandlerPageTables (
>> + VOID
>> + )
>> +{
>> + UINTN PoolPages;
>> + VOID *Buffer;
>> + VOID *Start;
>> + PAGE_MAP_AND_DIRECTORY_POINTER *PageMapLevel4Entry;
>> + PAGE_TABLE_1G_ENTRY *PageDirectory1GEntry;
>> + PAGE_TABLE_1G_ENTRY *Unenc1GEntry;
>> + UINT64 AddressEncMask;
>> +
>> + PoolPages = 1 + 10;
>> + Buffer = AllocateAlignedRuntimePages (PoolPages, PAGE_TABLE_POOL_ALIGNMENT);
>> + mPageTablePool = Buffer;
>> + mPageTablePool->NextPool = mPageTablePool;
>> + mPageTablePool->FreePages = PoolPages - 1;
>> + mPageTablePool->Offset = EFI_PAGES_TO_SIZE (1);
>> +
>> + Start = (UINT8 *)mPageTablePool + mPageTablePool->Offset;
>> + ZeroMem(Start, mPageTablePool->FreePages * EFI_PAGE_SIZE);
>> +
>> + AddressEncMask = 1ULL << 47;
>> +
>
> Preferably getting the encryption bit location from SEV CPUID
> information.
You're right; I'll fix.
>
>> + PageMapLevel4Entry = Start;
>> + PageDirectory1GEntry = (PAGE_TABLE_1G_ENTRY*)((UINT8*)Start + EFI_PAGE_SIZE);
>> + Unenc1GEntry = (PAGE_TABLE_1G_ENTRY*)((UINT8*)Start + 2 * EFI_PAGE_SIZE);
>> +
>> + PageMapLevel4Entry = Start;
>> + PageMapLevel4Entry += PML4_OFFSET(0x0ULL);
>> + PageMapLevel4Entry->Uint64 = (UINT64)PageDirectory1GEntry | AddressEncMask | 0x23;
>> +
>> + PageMapLevel4Entry = Start;
>> + PageMapLevel4Entry += PML4_OFFSET(UNENC_VIRT_ADDR_BASE); // should be 511
>> + PageMapLevel4Entry->Uint64 = (UINT64)Unenc1GEntry | AddressEncMask | 0x23;
>> +
>> + UINT64 PageAddr = 0;
>> + for (int i = 0; i < 512; i++, PageAddr += SIZE_1GB) {
>> + PAGE_TABLE_1G_ENTRY *e = PageDirectory1GEntry + i;
>> + e->Uint64 = PageAddr | AddressEncMask | 0xe3; // 1GB page
>> + }
>> +
>
> Changing encryption attributes of a page requires to flush it from
> the caches, you may need to do a clflush here.
Thanks for pointing that out. I think I didn't see that in the code that
builds the page tables for encrypted memory (which inspired most of this
function), but maybe I missed it.
Thanks,
Dov
>
> Thanks,
> Ashish
>
>> + UINT64 UnencPageAddr = 0;
>> + Unenc1GEntry->Uint64 = UnencPageAddr | 0xe3; // 1GB page unencrypted
>> +
>> + mMigrationHelperPageTables = (UINT64)Start | AddressEncMask;
>> +}
>> +
>> +VOID
>> +SwitchToMigrationHelperPageTables(VOID)
>> +{
>> + AsmWriteCr3(mMigrationHelperPageTables);
>> +}
>> +
>> +
>>
>> VOID
>> EFIAPI
>> @@ -56,7 +134,12 @@ MigrationHandlerMain (
>>
>> DebugPrint (DEBUG_INFO,"MIGRATION Handler Started\n");
>>
>> - params_base = PcdGet32 (PcdConfidentialMigrationMailboxBase);
>> + SwitchToMigrationHelperPageTables();
>> +
>> + //
>> + // Shared pages must be offset by UNENC_VIRT_ADDR_BASE.
>> + //
>> + params_base = PcdGet32 (PcdConfidentialMigrationMailboxBase) + UNENC_VIRT_ADDR_BASE;
>> params = (VOID *)params_base;
>> page_va = (VOID *)params_base + 0x1000;
>>
>> @@ -134,6 +217,8 @@ LaunchMigrationHandler (
>>
>> MigrationHandlerCpuIndex = NumProc - 1;
>>
>> + PrepareMigrationHandlerPageTables();
>> +
>> EFI_EVENT Event;
>> MpProto->GetProcessorInfo (MpProto, MigrationHandlerCpuIndex, &Tcb);
>> if (Tcb.StatusFlag != 7) {
>> @@ -154,6 +239,7 @@ LaunchMigrationHandler (
>> if (PcdGetBool(PcdIsConfidentialMigrationTarget)) {
>> DebugPrint (DEBUG_INFO,"Waiting for incoming confidential migration.\n");
>> DisableInterrupts ();
>> + SwitchToMigrationHelperPageTables();
>> CpuDeadLoop ();
>> }
>>
>> --
>> 2.20.1
>>
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