[PATCH v5 1/3] arm64: mm: Support Common Not Private translations

[vladimir.murzin@arm.com (Vladimir Murzin)]

On 27/07/18 12:35, Catalin Marinas wrote:
> Hi Vladimir,
> 
> On Tue, Jun 19, 2018 at 11:18:20AM +0100, Vladimir Murzin wrote:
>> diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
>> index 39ec0b8..c506fb7 100644
>> --- a/arch/arm64/include/asm/mmu_context.h
>> +++ b/arch/arm64/include/asm/mmu_context.h
>> @@ -149,6 +149,18 @@ static inline void cpu_replace_ttbr1(pgd_t *pgdp)
>>  
>>  	phys_addr_t pgd_phys = virt_to_phys(pgdp);
>>  
>> +	if (system_supports_cnp() && !WARN_ON(pgdp != lm_alias(swapper_pg_dir))) {
>> +		/*
>> +		 * cpu_replace_ttbr1() is used when there's a boot CPU
>> +		 * up (i.e. cpufeature framework is not up yet) and
>> +		 * latter only when we enable CNP via cpufeature's
>> +		 * enable() callback.
>> +		 * Also we rely on the cpu_hwcap bit being set before
>> +		 * calling the enable() function.
>> +		 */
>> +		pgd_phys |= TTBR_CNP_BIT;
>> +	}
>> +
>>  	replace_phys = (void *)__pa_symbol(idmap_cpu_replace_ttbr1);
> 
> So the above code sets the TTBR_CNP_BIT (bit 0) in pgd_phys and calls
> the idmap_cpu_replace_ttbr1() with this value. Looking at the latter, it
> performs a phys_to_ttbr transformation of pgd_phys which masks out the
> bottom 2 bits when CONFIG_ARM64_PA_BITS_52 is enabled. I think we need
> to tweak TTBR_BADDR_MASK_52 to start from bit 0.
> 
> (cc'ing Kristina as she added this code, in case there is any issue with
> extending the mask)
> 

Something like bellow?

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 0bcc98d..e0b4b2f 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -524,11 +524,10 @@ USER(\label, ic	ivau, \tmp2)			// invalidate I line PoU
  * 	ttbr:	returns the TTBR value
  */
 	.macro	phys_to_ttbr, ttbr, phys
-#ifdef CONFIG_ARM64_PA_BITS_52
-	orr	\ttbr, \phys, \phys, lsr #46
-	and	\ttbr, \ttbr, #TTBR_BADDR_MASK_52
-#else
 	mov	\ttbr, \phys
+#ifdef CONFIG_ARM64_PA_BITS_52
+	ubfx	\ttbr, \ttbr, #48, #4
+	orr	\ttbr, \phys, \ttbr, lsl #2
 #endif
 	.endm
 
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 1bdeca8..1b9d0e9 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -770,7 +770,7 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
 #define kc_offset_to_vaddr(o)	((o) | VA_START)
 
 #ifdef CONFIG_ARM64_PA_BITS_52
-#define phys_to_ttbr(addr)	(((addr) | ((addr) >> 46)) & TTBR_BADDR_MASK_52)
+#define phys_to_ttbr(addr)	((addr) | (((addr) >> 46) & TTBR_BADDR_MASK_52))
 #else
 #define phys_to_ttbr(addr)	(addr)
 #endif


Vladimir