Re: [kvm-unit-tests PATCH 1/2] arm64: set sctlr_el1.SPAN

[Shaoqin Huang <shahuang@redhat.com>]

Hi,

On 7/14/23 18:31, Alexandru Elisei wrote:
> Hi,
> 
> On Sat, Jun 17, 2023 at 01:31:37AM +0000, Nadav Amit wrote:
>> From: Nadav Amit <namit@vmware.com>
>>
>> Do not assume PAN is not supported or that sctlr_el1.SPAN is already set.
> 
> In arm/cstart64.S
> 
> .globl start
> start:
>          /* get our base address */
> 	[..]
> 
> 1:
>          /* zero BSS */
> 	[..]
> 
>          /* zero and set up stack */
> 	[..]
> 
>          /* set SCTLR_EL1 to a known value */
>          ldr     x4, =INIT_SCTLR_EL1_MMU_OFF
> 	[..]
> 
>          /* set up exception handling */
>          bl      exceptions_init
> 	[..]
> 
> Where in lib/arm64/asm/sysreg.h:
> 
> #define SCTLR_EL1_RES1  (_BITUL(7) | _BITUL(8) | _BITUL(11) | _BITUL(20) | \
>                           _BITUL(22) | _BITUL(23) | _BITUL(28) | _BITUL(29))
> #define INIT_SCTLR_EL1_MMU_OFF  \
>                          SCTLR_EL1_RES1
> 
> Look like bit 23 (SPAN) should be set.
> 
> How are you seeing SCTLR_EL1.SPAN unset?

Yeah. the sctlr_el1.SPAN has always been set by the above flow. So Nadav 
you can describe what you encounter with more details. Like which tests 
crash you encounter, and how to reproduce it.

Thanks,
Shaoqin

> 
> Thanks,
> Alex
> 
>>
>> Without setting sctlr_el1.SPAN, tests crash when they access the memory
>> after an exception.
>>
>> Signed-off-by: Nadav Amit <namit@vmware.com>
>> ---
>>   arm/cstart64.S         | 1 +
>>   lib/arm64/asm/sysreg.h | 1 +
>>   2 files changed, 2 insertions(+)
>>
>> diff --git a/arm/cstart64.S b/arm/cstart64.S
>> index 61e27d3..d4cee6f 100644
>> --- a/arm/cstart64.S
>> +++ b/arm/cstart64.S
>> @@ -245,6 +245,7 @@ asm_mmu_enable:
>>   	orr	x1, x1, SCTLR_EL1_C
>>   	orr	x1, x1, SCTLR_EL1_I
>>   	orr	x1, x1, SCTLR_EL1_M
>> +	orr	x1, x1, SCTLR_EL1_SPAN
>>   	msr	sctlr_el1, x1
>>   	isb
>>   
>> diff --git a/lib/arm64/asm/sysreg.h b/lib/arm64/asm/sysreg.h
>> index 18c4ed3..b9868ff 100644
>> --- a/lib/arm64/asm/sysreg.h
>> +++ b/lib/arm64/asm/sysreg.h
>> @@ -81,6 +81,7 @@ asm(
>>   
>>   /* System Control Register (SCTLR_EL1) bits */
>>   #define SCTLR_EL1_EE	(1 << 25)
>> +#define SCTLR_EL1_SPAN	(1 << 23)
>>   #define SCTLR_EL1_WXN	(1 << 19)
>>   #define SCTLR_EL1_I	(1 << 12)
>>   #define SCTLR_EL1_SA0	(1 << 4)
>> -- 
>> 2.34.1
>>
>>
> 

-- 
Shaoqin