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OvmfPkg/IoMmuDxe: don't rely on TPLs to manage concurrency 

Instead of relying on raising the TPL to protect the critical sections
that manipulate the global bitmask that keeps track of bounce buffer
allocations, use compare-and-exchange to manage the global variable, and
tweak the logic to line up with that.

Given that IoMmuDxe implements a singleton protocol that is shared
between multiple drivers, and considering the elaborate and confusing
requirements in the UEFP spec regarding TPL levels at which protocol
methods may be invoked, not relying on TPL levels at all is a more
robust approach in this case.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=2211060
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Pedro Falcato <pedro.falcato@gmail.com>
This commit is contained in:
Ard Biesheuvel 2023-07-20 15:45:57 +02:00 committed by mergify[bot]
parent beafabdae4
commit dfb941d32a
2 changed files with 61 additions and 42 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

102
OvmfPkg/IoMmuDxe/IoMmuBuffer.c
View File

@ -12,6 +12,7 @@
#include <Library/MemEncryptSevLib.h>
#include <Library/MemEncryptTdxLib.h>
#include <Library/PcdLib.h>
#include <Library/SynchronizationLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include "IoMmuInternal.h"
@ -268,16 +269,17 @@ InternalAllocateBuffer (
IN EFI_ALLOCATE_TYPE Type,
IN EFI_MEMORY_TYPE MemoryType,
IN UINTN Pages,
IN OUT UINT32 *ReservedMemBitmap,
OUT UINT32 *ReservedMemBit,
IN OUT EFI_PHYSICAL_ADDRESS *PhysicalAddress
)
{
UINT32 MemBitmap;
UINT32 ReservedMemBitmap;
UINT8 Index;
IOMMU_RESERVED_MEM_RANGE *MemRange;
UINTN PagesOfLastMemRange;
*ReservedMemBitmap = 0;
*ReservedMemBit = 0;
if (Pages == 0) {
ASSERT (FALSE);
@ -309,23 +311,31 @@ InternalAllocateBuffer (
MemRange = &mReservedMemRanges[Index];
if ((mReservedMemBitmap & MemRange->BitmapMask) == MemRange->BitmapMask) {
// The reserved memory is exausted. Turn to legacy allocate.
goto LegacyAllocateBuffer;
}
do {
ReservedMemBitmap = mReservedMemBitmap;
MemBitmap = (mReservedMemBitmap & MemRange->BitmapMask) >> MemRange->Shift;
for (Index = 0; Index < MemRange->Slots; Index++) {
if ((MemBitmap & (UINT8)(1<<Index)) == 0) {
break;
if ((ReservedMemBitmap & MemRange->BitmapMask) == MemRange->BitmapMask) {
// The reserved memory is exhausted. Turn to legacy allocate.
goto LegacyAllocateBuffer;
}
}
ASSERT (Index != MemRange->Slots);
MemBitmap = (ReservedMemBitmap & MemRange->BitmapMask) >> MemRange->Shift;
*PhysicalAddress = MemRange->StartAddressOfMemRange + Index * SIZE_OF_MEM_RANGE (MemRange) + MemRange->HeaderSize;
*ReservedMemBitmap = (UINT32)(1 << (Index + MemRange->Shift));
for (Index = 0; Index < MemRange->Slots; Index++) {
if ((MemBitmap & (UINT8)(1<<Index)) == 0) {
break;
}
}
ASSERT (Index != MemRange->Slots);
*PhysicalAddress = MemRange->StartAddressOfMemRange + Index * SIZE_OF_MEM_RANGE (MemRange) + MemRange->HeaderSize;
*ReservedMemBit = (UINT32)(1 << (Index + MemRange->Shift));
} while (ReservedMemBitmap != InterlockedCompareExchange32 (
&mReservedMemBitmap,
ReservedMemBitmap,
ReservedMemBitmap | *ReservedMemBit
));
DEBUG ((
DEBUG_VERBOSE,
@ -334,16 +344,16 @@ InternalAllocateBuffer (
MemRange->DataSize,
*PhysicalAddress,
Pages,
*ReservedMemBitmap,
mReservedMemBitmap,
mReservedMemBitmap | *ReservedMemBitmap
*ReservedMemBit,
ReservedMemBitmap,
ReservedMemBitmap | *ReservedMemBit
));
return EFI_SUCCESS;
LegacyAllocateBuffer:
*ReservedMemBitmap = 0;
*ReservedMemBit = 0;
return gBS->AllocatePages (Type, MemoryType, Pages, PhysicalAddress);
}
@ -366,27 +376,41 @@ IoMmuAllocateBounceBuffer (
)
{
EFI_STATUS Status;
UINT32 ReservedMemBitmap;
EFI_TPL OldTpl;
OldTpl = gBS->RaiseTPL (TPL_NOTIFY);
ReservedMemBitmap = 0;
Status = InternalAllocateBuffer (
Type,
MemoryType,
MapInfo->NumberOfPages,
&ReservedMemBitmap,
&MapInfo->PlainTextAddress
);
MapInfo->ReservedMemBitmap = ReservedMemBitmap;
mReservedMemBitmap |= ReservedMemBitmap;
gBS->RestoreTPL (OldTpl);
Status = InternalAllocateBuffer (
Type,
MemoryType,
MapInfo->NumberOfPages,
&MapInfo->ReservedMemBitmap,
&MapInfo->PlainTextAddress
);
ASSERT (Status == EFI_SUCCESS);
return Status;
}
/**
* Clear a bit in the reserved memory bitmap in a thread safe manner
*
* @param ReservedMemBit The bit to clear
*/
STATIC
VOID
ClearReservedMemBit (
IN UINT32 ReservedMemBit
)
{
UINT32 ReservedMemBitmap;
do {
ReservedMemBitmap = mReservedMemBitmap;
} while (ReservedMemBitmap != InterlockedCompareExchange32 (
&mReservedMemBitmap,
ReservedMemBitmap,
ReservedMemBitmap & ~ReservedMemBit
));
}
/**
* Free the bounce buffer allocated in IoMmuAllocateBounceBuffer.
*
@ -398,8 +422,6 @@ IoMmuFreeBounceBuffer (
IN OUT MAP_INFO *MapInfo
)
{
EFI_TPL OldTpl;
if (MapInfo->ReservedMemBitmap == 0) {
gBS->FreePages (MapInfo->PlainTextAddress, MapInfo->NumberOfPages);
} else {
@ -412,11 +434,9 @@ IoMmuFreeBounceBuffer (
mReservedMemBitmap,
mReservedMemBitmap & ((UINT32)(~MapInfo->ReservedMemBitmap))
));
OldTpl = gBS->RaiseTPL (TPL_NOTIFY);
ClearReservedMemBit (MapInfo->ReservedMemBitmap);
MapInfo->PlainTextAddress = 0;
mReservedMemBitmap &= (UINT32)(~MapInfo->ReservedMemBitmap);
MapInfo->ReservedMemBitmap = 0;
gBS->RestoreTPL (OldTpl);
}
return EFI_SUCCESS;
@ -452,8 +472,6 @@ IoMmuAllocateCommonBuffer (
);
ASSERT (Status == EFI_SUCCESS);
mReservedMemBitmap |= *ReservedMemBitmap;
if (*ReservedMemBitmap != 0) {
*PhysicalAddress -= SIZE_4KB;
}
@ -494,7 +512,7 @@ IoMmuFreeCommonBuffer (
mReservedMemBitmap & ((UINT32)(~CommonBufferHeader->ReservedMemBitmap))
));
mReservedMemBitmap &= (UINT32)(~CommonBufferHeader->ReservedMemBitmap);
ClearReservedMemBit (CommonBufferHeader->ReservedMemBitmap);
return EFI_SUCCESS;
LegacyFreeCommonBuffer:

1
OvmfPkg/IoMmuDxe/IoMmuDxe.inf
View File

@ -35,6 +35,7 @@
MemEncryptSevLib
MemEncryptTdxLib
MemoryAllocationLib
SynchronizationLib
UefiBootServicesTableLib
UefiDriverEntryPoint