Re: [PATCH 01/11] Initialize the mapping of KASan shadow memory

[Liuwenliang (Abbott Liu)]

On 09/11/17  18:36 Marc Zyngier [mailto:marc.zyngier@xxxxxxx] wrote:
>On Wed, Nov 15 2017 at 10:20:02 am GMT, "Liuwenliang (Abbott Liu)" <liuwenliang@xxxxxxxxxx> wrote:
>> On 09/11/17 18:11, Marc Zyngier [mailto:marc.zyngier@xxxxxxx] wrote:
>>>On 09/11/17 07:46, Liuwenliang (Abbott Liu) wrote:
>>>> diff --git a/arch/arm/mm/kasan_init.c b/arch/arm/mm/kasan_init.c
>>>> index 049ee0a..359a782 100644
>>>> --- a/arch/arm/mm/kasan_init.c
>>>> +++ b/arch/arm/mm/kasan_init.c
>>>> @@ -15,6 +15,7 @@
>>>>  #include <asm/proc-fns.h>
>>>>  #include <asm/tlbflush.h>
>>>>  #include <asm/cp15.h>
>>>> +#include <asm/kvm_hyp.h>
>>>
>>>No, please don't do that. You shouldn't have to include KVM stuff in
>>>unrelated code. Instead of adding stuff to kvm_hyp.h, move all the
>>>__ACCESS_CP15* to cp15.h, and it will be obvious to everyone that this
>>>is where new definition should be added.
>>
>> Thanks for your review.  You are right. It is better to move
>> __ACCESS_CP15* to cp15.h than to include kvm_hyp.h. But I don't think
>> it is a good idea to move registers definition which is used in
>> virtualization to cp15.h, Because there is no virtualization stuff in
>> cp15.h.
>
>It is not about virtualization at all.
>
>It is about what is a CP15 register and what is not. This file is called
>"cp15.h", not "cp15-except-virtualization-and-maybe-some-others.h". But
>at the end of the day, that's for Russell to decide.

Thanks for your review.
You are right, all __ACCESS_CP15* are cp15 registers. I splited normal cp15 register
(such as TTBR0/TTBR1/SCTLR and so on) and virtualizaton cp15 registers(such as VTTBR/
CNTV_CVAL/HCR) because I didn't think we need use those virtualization cp15 registers
in non virtualization system.

But now I think all __ACCESS_CP15* move to cp15.h may be a better choise. 

>>
>> Here is the code which I tested on vexpress_a15 and vexpress_a9:
>> diff --git a/arch/arm/include/asm/cp15.h b/arch/arm/include/asm/cp15.h
>> index dbdbce1..6db1f51 100644
>> --- a/arch/arm/include/asm/cp15.h
>> +++ b/arch/arm/include/asm/cp15.h
>> @@ -64,6 +64,43 @@
>>  #define __write_sysreg(v, r, w, c, t)  asm volatile(w " " c : : "r" ((t)(v)))
>>  #define write_sysreg(v, ...)           __write_sysreg(v, __VA_ARGS__)
>>
>> +#ifdef CONFIG_ARM_LPAE
>> +#define TTBR0           __ACCESS_CP15_64(0, c2)
>> +#define TTBR1           __ACCESS_CP15_64(1, c2)
>> +#define PAR             __ACCESS_CP15_64(0, c7)
>> +#else
>> +#define TTBR0           __ACCESS_CP15(c2, 0, c0, 0)
>> +#define TTBR1           __ACCESS_CP15(c2, 0, c0, 1)
>> +#define PAR             __ACCESS_CP15(c7, 0, c4, 0)
>> +#endif
>
>Again: there is no point in not having these register encodings
>cohabiting. They are both perfectly defined in the architecture. Just
>suffix one (or even both) with their respective size, making it obvious
>which one you're talking about.

I am sorry that I didn't point why I need to define TTBR0/ TTBR1/PAR in to different way
between CONFIG_ARM_LPAE and non CONFIG_ARM_LPAE.
The following description is the reason:
Here is the description come from DDI0406C2c_arm_architecture_reference_manual.pdf:

B4.1.155 TTBR0, Translation Table Base Register 0, VMSA
...
The Multiprocessing Extensions change the TTBR0 32-bit register format.
The Large Physical Address Extension extends TTBR0 to a 64-bit register. In an
implementation that includes the Large Physical Address Extension, TTBCR.EAE
determines which TTBR0 format is used:
EAE==0 32-bit format is used. TTBR0[63:32] are ignored.
EAE==1 64-bit format is used.

B4.1.156 TTBR1, Translation Table Base Register 1, VMSA
...
The Multiprocessing Extensions change the TTBR0 32-bit register format.
The Large Physical Address Extension extends TTBR1 to a 64-bit register. In an
implementation that includes the Large Physical Address Extension, TTBCR.EAE
determines which TTBR1 format is used:
EAE==0 32-bit format is used. TTBR1[63:32] are ignored.
EAE==1 64-bit format is used.

B4.1.154 TTBCR, Translation Table Base Control Register, VMSA
...
EAE, bit[31], if implementation includes the Large Physical Address Extension
Extended Address Enable. The meanings of the possible values of this bit are:
0   Use the 32-bit translation system, with the Short-descriptor translation table format. In
this case, the format of the TTBCR is as described in this section.
1   Use the 40-bit translation system, with the Long-descriptor translation table format. In
this case, the format of the TTBCR is as described in TTBCR format when using the
Long-descriptor translation table format on page B4-1692.

B4.1.112 PAR, Physical Address Register, VMSA
If the implementation includes the Large Physical Address Extension, the PAR is extended
to be a 64-bit register and:
* The 64-bit PAR is used:
- when using the Long-descriptor translation table format
- in an implementation that includes the Virtualization Extensions, for the result
of an ATS1Cxx operation performed from Hyp mode.
* The 32-bit PAR is used when using the Short-descriptor translation table format. In
this case, PAR[63:32] is UNK/SBZP.
Otherwise, the PAR is a 32-bit register.