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ArmPkg/ArmMmuLib: drop pointless LookupAddresstoRootTable() routine 

LookupAddresstoRootTable() uses a loop to go over its MaxAddress
argument, essentially to do a log2() and determine how many bits are
needed to represent it. Since the argument is the result of a shift-left
expression, there is some room for improvement here, and we can simply
use the bit count directly to calculate the value of T0SZ. At the same
time, we can omit calling GetRootTranslationTableInfo() to determine the
number of root table entries, and add a new helper that applies the
trivial calculation directly.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
Reviewed-by: Leif Lindholm <leif@nuviainc.com>
This commit is contained in:
Ard Biesheuvel 2020-03-31 19:25:02 +02:00 committed by mergify[bot]
parent 49188b2aa4
commit db0f8c2f84
1 changed files with 15 additions and 34 deletions
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49
ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
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@ -59,6 +59,16 @@ ArmMemoryAttributeToPageAttribute (
#define MIN_T0SZ 16
#define BITS_PER_LEVEL 9
#define MAX_VA_BITS 48
STATIC
UINTN
GetRootTableEntryCount (
IN UINTN T0SZ
)
{
return TT_ENTRY_COUNT >> (T0SZ - MIN_T0SZ) % BITS_PER_LEVEL;
}
VOID
GetRootTranslationTableInfo (
@ -284,36 +294,6 @@ UpdateRegionMappingRecursive (
return EFI_SUCCESS;
}
STATIC
VOID
LookupAddresstoRootTable (
IN UINT64 MaxAddress,
OUT UINTN *T0SZ,
OUT UINTN *TableEntryCount
)
{
UINTN TopBit;
// Check the parameters are not NULL
ASSERT ((T0SZ != NULL) && (TableEntryCount != NULL));
// Look for the highest bit set in MaxAddress
for (TopBit = 63; TopBit != 0; TopBit--) {
if ((1ULL << TopBit) & MaxAddress) {
// MaxAddress top bit is found
TopBit = TopBit + 1;
break;
}
}
ASSERT (TopBit != 0);
// Calculate T0SZ from the top bit of the MaxAddress
*T0SZ = 64 - TopBit;
// Get the Table info from T0SZ
GetRootTranslationTableInfo (*T0SZ, NULL, TableEntryCount);
}
STATIC
EFI_STATUS
UpdateRegionMapping (
@ -508,6 +488,7 @@ ArmConfigureMmu (
)
{
VOID* TranslationTable;
UINTN MaxAddressBits;
UINT64 MaxAddress;
UINTN T0SZ;
UINTN RootTableEntryCount;
@ -526,11 +507,11 @@ ArmConfigureMmu (
// into account the architectural limitations that result from UEFI's
// use of 4 KB pages.
//
MaxAddress = MIN (LShiftU64 (1ULL, ArmGetPhysicalAddressBits ()) - 1,
MAX_ALLOC_ADDRESS);
MaxAddressBits = MIN (ArmGetPhysicalAddressBits (), MAX_VA_BITS);
MaxAddress = LShiftU64 (1ULL, MaxAddressBits) - 1;
// Lookup the Table Level to get the information
LookupAddresstoRootTable (MaxAddress, &T0SZ, &RootTableEntryCount);
T0SZ = 64 - MaxAddressBits;
RootTableEntryCount = GetRootTableEntryCount (T0SZ);
//
// Set TCR that allows us to retrieve T0SZ in the subsequent functions