Re: [Qemu-devel] AArch64 QEMU System emulation: issue with TTBR0

[Claudio Fontana]

On 03.06.2014 11:34, Rob Herring wrote:
> On Mon, Jun 2, 2014 at 11:16 AM, Claudio Fontana <address@hidden> wrote:
>> Hello Peter,
>>
>> I am porting OSv to AArch64, and I have some working code running on
>> the Foundation Models,
>> where I run qemu natively with --enable-kvm,
>>
>> which does not seem to work when run instead on top of the system emulation.
>>
>> In particular I get a sync exception when I try to msr to TTBR0_EL1.
> 
> How are you configuring TCR register?

https://github.com/cloudius-systems/osv/blob/master/arch/aarch64/boot.S

contains more context, the register itself is initialized as such:
        ldr x0, =0x15b5103510
        msr tcr_el1, x0
        isb

all bits used are explained in a comment in the boot.S above.

Thanks,

Claudio
> 
> Rob
> 
>>
>> The ESR as read in env->cp15.esr_el[1] is 0x8400000e, which looking up
>> in the ESR table means
>>
>> Instruction fault, with IFSC (instruction fault status code) = 0xe,
>> which should match
>>
>> 0b0011LL = permission fault (LL indicates level at which fault occurred).
>>
>> with LL = 0b10 meaning EL2.
>>
>> The code is in particular:
>>
>> 00000000401db2d0 <mmu::switch_to_runtime_page_tables()>:
>>     401db2d0:   d00037a0        adrp    x0, 408d1000 <unique_mtx+0x10>
>>     401db2d4:   9130e000        add     x0, x0, #0xc38
>>     401db2d8:   f9400000        ldr     x0, [x0]
>>     401db2dc:   92748c00        and     x0, x0, #0xfffffffff000
>>     401db2e0:   d5182000        msr     ttbr0_el1, x0
>>     401db2e4:   d5033fdf        isb
>>     401db2e8:   d00037a0        adrp    x0, 408d1000 <unique_mtx+0x10>
>>     401db2ec:   9130e000        add     x0, x0, #0xc38
>>     401db2f0:   f9400400        ldr     x0, [x0,#8]
>>     401db2f4:   92748c00        and     x0, x0, #0xfffffffff000
>>     401db2f8:   d5182020        msr     ttbr1_el1, x0
>>     401db2fc:   d5033fdf        isb
>>     401db300:   d5033f9f        dsb     sy
>>     401db304:   d508831f        tlbi    vmalle1is
>>     401db308:   d5033f9f        dsb     sy
>>     401db30c:   d5033fdf        isb
>>     401db310:   d65f03c0        ret
>>
>> ELR_EL1 in env->elr_el[1] reads as 0x401da200, which is strangely
>> enough the address of the first instruction of the exception vector
>> entry for sync:
>>
>>         ...
>>     401da200:   14000169        b       401da7a4 <entry_sync>
>>     401da204:   d503201f        nop
>>         ...
>>     401da280:   14000174        b       401da850 <entry_irq>
>>     401da284:   d503201f        nop
>>
>> The source is available at:
>>
>> https://github.com/cloudius-systems/osv/blob/master/arch/aarch64/mmu.cc
>>
>> Thanks for any advice,
>>
>> Claudio
>>
>