On 7/14/21 9:08 PM, Steven Price wrote:
> On 14/07/2021 03:21, Anshuman Khandual wrote:
>> FEAT_LPA2 requires different PTE representation formats for both 4K and 16K
>> page size config. This adds FEAT_LPA2 specific new PTE encodings as per ARM
>> ARM (0487G.A) which updates [pte|phys]_to_[phys|pte](). The updated helpers
>> would be used when FEAT_LPA2 gets enabled via CONFIG_ARM64_PA_BITS_52 on 4K
>> and 16K page size. Although TTBR encoding and phys_to_ttbr() helper remains
>> the same as FEAT_LPA for FEAT_LPA2 as well. It updates 'phys_to_pte' helper
>> to accept a temporary variable and changes impacted call sites.
>>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
>> ---
>> arch/arm64/include/asm/assembler.h | 23 +++++++++++++++++++----
>> arch/arm64/include/asm/pgtable-hwdef.h | 4 ++++
>> arch/arm64/include/asm/pgtable.h | 4 ++++
>> arch/arm64/kernel/head.S | 25 +++++++++++++------------
>> 4 files changed, 40 insertions(+), 16 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
>> index fedc202..0492543 100644
>> --- a/arch/arm64/include/asm/assembler.h
>> +++ b/arch/arm64/include/asm/assembler.h
>> @@ -606,7 +606,7 @@ alternative_endif
>> #endif
>> .endm
>>
>> - .macro phys_to_pte, pte, phys
>> + .macro phys_to_pte, pte, phys, tmp
>> #ifdef CONFIG_ARM64_PA_BITS_52_LPA
>> /*
>> * We assume \phys is 64K aligned and this is guaranteed by only
>> @@ -614,6 +614,17 @@ alternative_endif
>> */
>> orr \pte, \phys, \phys, lsr #36
>> and \pte, \pte, #PTE_ADDR_MASK
>> +#elif defined(CONFIG_ARM64_PA_BITS_52_LPA2)
>> + orr \pte, \phys, \phys, lsr #42
>> +
>> + /*
>> + * The 'tmp' is being used here to just prepare
>> + * and hold PTE_ADDR_MASK which cannot be passed
>> + * to the subsequent 'and' instruction.
>> + */
>> + mov \tmp, #PTE_ADDR_LOW
>> + orr \tmp, \tmp, #PTE_ADDR_HIGH
>> + and \pte, \pte, \tmp
> Rather than adding an extra temporary register (and the fallout of
> various other macros needing an extra register), this can be done with
> two AND instructions:
I would really like to get rid of the 'tmp' variable here as
well but did not figure out any method of accomplishing it.
>
> /* PTE_ADDR_MASK cannot be encoded as an immediate, so
> * mask off all but two bits, followed by masking the
> * extra two bits
> */
> and \pte, \pte, #PTE_ADDR_MASK | (3 << 10)
> and \pte, \pte, #~(3 << 10)
Did this change as suggested
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -626,9 +626,8 @@ alternative_endif
* and hold PTE_ADDR_MASK which cannot be passed
* to the subsequent 'and' instruction.
*/
- mov \tmp, #PTE_ADDR_LOW
- orr \tmp, \tmp, #PTE_ADDR_HIGH
- and \pte, \pte, \tmp
+ and \pte, \pte, #PTE_ADDR_MASK | (0x3 << 10)
+ and \pte, \pte, #~(0x3 << 10)
.Lskip_lpa2\@:
mov \pte, \phys
but still fails to build (tested on 16K)
arch/arm64/kernel/head.S: Assembler messages:
arch/arm64/kernel/head.S:377: Error: immediate out of range at operand 3 -- `and x6,x6,#((((1<<(50-14))-1)<<14)|(0x3<<8))|(0x3<<10)'
arch/arm64/kernel/head.S:390: Error: immediate out of range at operand 3 -- `and x12,x12,#((((1<<(50-14))-1)<<14)|(0x3<<8))|(0x3<<10)'
arch/arm64/kernel/head.S:390: Error: immediate out of range at operand 3 -- `and x12,x12,#((((1<<(50-14))-1)<<14)|(0x3<<8))|(0x3<<10)'
arch/arm64/kernel/head.S:404: Error: immediate out of range at operand 3 -- `and x12,x12,#((((1<<(50-14))-1)<<14)|(0x3<<8))|(0x3<<10)'
arch/arm64/kernel/head.S:404: Error: immediate out of range at operand 3 -- `and x12,x12,#((((1<<(50-14))-1)<<14)|(0x3<<8))|(0x3<<10)'
