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ArmPkg/ArmMmuLib: use a pool allocation for the root table 

Currently, we allocate a full page for the root translation table, even
if the configured translation only requires two entries (16 bytes) for
the root level, which happens to be the case for a 40 bit VA. Likewise,
for a 36-bit VA space, the root table only needs 16 entries of 8 bytes
each, adding up to 128 bytes.

So switch to a pool allocation for the root table if we can, but take into
account that the architecture requires it to be naturally aligned to its
size, i.e., a 64 byte table requires 64 byte alignment, whereas pool
allocations in general are only guaranteed to be aligned to 8 bytes.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
This commit is contained in:
Ard Biesheuvel 2016-09-09 09:50:21 +01:00
parent 674e127ef6
commit d32702d2c2
1 changed files with 22 additions and 5 deletions
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23
ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
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@ -553,12 +553,14 @@ ArmConfigureMmu (
)
{
VOID* TranslationTable;
VOID* TranslationTableBuffer;
UINT32 TranslationTableAttribute;
ARM_MEMORY_REGION_DESCRIPTOR *MemoryTableEntry;
UINT64 MaxAddress;
UINT64 TopAddress;
UINTN T0SZ;
UINTN RootTableEntryCount;
UINTN RootTableEntrySize;
UINT64 TCR;
RETURN_STATUS Status;
@ -638,8 +640,19 @@ ArmConfigureMmu (
// Set TCR
ArmSetTCR (TCR);
// Allocate pages for translation table
// Allocate pages for translation table. Pool allocations are 8 byte aligned,
// but we may require a higher alignment based on the size of the root table.
RootTableEntrySize = RootTableEntryCount * sizeof(UINT64);
if (RootTableEntrySize < EFI_PAGE_SIZE / 2) {
TranslationTableBuffer = AllocatePool (2 * RootTableEntrySize - 8);
//
// Naturally align the root table. Preserves possible NULL value
//
TranslationTable = (VOID *)((UINTN)(TranslationTableBuffer - 1) | (RootTableEntrySize - 1)) + 1;
} else {
TranslationTable = AllocatePages (1);
TranslationTableBuffer = NULL;
}
if (TranslationTable == NULL) {
return RETURN_OUT_OF_RESOURCES;
}
@ -653,10 +666,10 @@ ArmConfigureMmu (
}
if (TranslationTableSize != NULL) {
*TranslationTableSize = RootTableEntryCount * sizeof(UINT64);
*TranslationTableSize = RootTableEntrySize;
}
ZeroMem (TranslationTable, RootTableEntryCount * sizeof(UINT64));
ZeroMem (TranslationTable, RootTableEntrySize);
// Disable MMU and caches. ArmDisableMmu() also invalidates the TLBs
ArmDisableMmu ();
@ -716,7 +729,11 @@ ArmConfigureMmu (
return RETURN_SUCCESS;
FREE_TRANSLATION_TABLE:
if (TranslationTableBuffer != NULL) {
FreePool (TranslationTableBuffer);
} else {
FreePages (TranslationTable, 1);
}
return Status;
}