From: "Ard Biesheuvel" <ardb@kernel.org>
To: devel@edk2.groups.io
Cc: Ard Biesheuvel <ardb@kernel.org>,
Gerd Hoffmann <kraxel@redhat.com>,
Jiewen Yao <jiewen.yao@intel.com>, Michael Brown <mcb30@ipxe.org>
Subject: [edk2-devel] [RFC/RFT PATCH] OvmfPkg/IoMmuDxe: don't rely on TPLs for re-entrancy
Date: Thu, 20 Jul 2023 15:45:57 +0200 [thread overview]
Message-ID: <20230720134557.3903923-1-ardb@kernel.org> (raw)
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.
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael Brown <mcb30@ipxe.org>
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2211060
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
OvmfPkg/IoMmuDxe/IoMmuBuffer.c | 100 ++++++++++++--------
OvmfPkg/IoMmuDxe/IoMmuDxe.inf | 1 +
2 files changed, 60 insertions(+), 41 deletions(-)
diff --git a/OvmfPkg/IoMmuDxe/IoMmuBuffer.c b/OvmfPkg/IoMmuDxe/IoMmuBuffer.c
index 103003cae376b93f..2764c35044ac23a7 100644
--- a/OvmfPkg/IoMmuDxe/IoMmuBuffer.c
+++ b/OvmfPkg/IoMmuDxe/IoMmuBuffer.c
@@ -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;
+ if ((ReservedMemBitmap & MemRange->BitmapMask) == MemRange->BitmapMask) {
+ // The reserved memory is exhausted. Turn to legacy allocate.
+ goto LegacyAllocateBuffer;
+ }
+
+ MemBitmap = (ReservedMemBitmap & MemRange->BitmapMask) >> MemRange->Shift;
- for (Index = 0; Index < MemRange->Slots; Index++) {
- if ((MemBitmap & (UINT8)(1<<Index)) == 0) {
- break;
+ for (Index = 0; Index < MemRange->Slots; Index++) {
+ if ((MemBitmap & (UINT8)(1<<Index)) == 0) {
+ break;
+ }
}
- }
- ASSERT (Index != MemRange->Slots);
+ ASSERT (Index != MemRange->Slots);
- *PhysicalAddress = MemRange->StartAddressOfMemRange + Index * SIZE_OF_MEM_RANGE (MemRange) + MemRange->HeaderSize;
- *ReservedMemBitmap = (UINT32)(1 << (Index + MemRange->Shift));
+ *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);
MapInfo->PlainTextAddress = 0;
- mReservedMemBitmap &= (UINT32)(~MapInfo->ReservedMemBitmap);
+ ClearReservedMemBit (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:
diff --git a/OvmfPkg/IoMmuDxe/IoMmuDxe.inf b/OvmfPkg/IoMmuDxe/IoMmuDxe.inf
index 17fca52856925da0..d08f7e59e2b665f4 100644
--- a/OvmfPkg/IoMmuDxe/IoMmuDxe.inf
+++ b/OvmfPkg/IoMmuDxe/IoMmuDxe.inf
@@ -35,6 +35,7 @@ [LibraryClasses]
MemEncryptSevLib
MemEncryptTdxLib
MemoryAllocationLib
+ SynchronizationLib
UefiBootServicesTableLib
UefiDriverEntryPoint
--
2.39.2
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next reply other threads:[~2023-07-20 13:46 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-20 13:45 Ard Biesheuvel [this message]
2023-07-21 22:55 ` [edk2-devel] [RFC/RFT PATCH] OvmfPkg/IoMmuDxe: don't rely on TPLs for re-entrancy Pedro Falcato
2023-07-24 14:21 ` Ard Biesheuvel
2023-07-24 17:08 ` Pedro Falcato
2023-08-22 6:25 ` Gerd Hoffmann
2023-08-22 7:57 ` Ard Biesheuvel
2023-08-23 11:07 ` Gerd Hoffmann
2023-08-23 15:11 ` Ard Biesheuvel
2023-08-23 17:18 ` Gerd Hoffmann
2023-08-23 18:10 ` Pedro Falcato
2023-08-24 8:06 ` Gerd Hoffmann
2023-08-24 10:31 ` Ard Biesheuvel
2023-08-28 9:16 ` Gerd Hoffmann
2023-08-28 11:13 ` Ard Biesheuvel
2023-08-31 16:01 ` Ard Biesheuvel
2023-09-04 11:45 ` Gerd Hoffmann
2023-09-04 12:06 ` Ard Biesheuvel
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