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Re: [Qemu-devel] [PATCH 11/14] target-arm: Extend FP checks to use an EL

From: Peter Maydell
Subject: Re: [Qemu-devel] [PATCH 11/14] target-arm: Extend FP checks to use an EL
Date: Thu, 28 May 2015 14:19:42 +0100

On 28 May 2015 at 13:50, Edgar E. Iglesias <address@hidden> wrote:
> On Tue, May 19, 2015 at 07:33:31PM +0100, Peter Maydell wrote:
>> +    /* For the CPTR registers we don't need to guard with an ARM_FEATURE
>> +     * check because zero bits in the registers mean "don't trap".
>> +     */
>> +
>> +    /* CPTR_EL2 : present in v7VE or v8 */
>> +    if (cur_el <= 2 && extract32(env->cp15.cptr_el[2], 10, 1)
>> +        && arm_is_secure_below_el3(env)) {
> I think this should be !arm_is_secure_below_el3(env)


> Also the ARMv7 manual, the part describing CPACR cpn bits, indicates that
> HCTPR has prio over CPACR. I didn't find any thing like that for
> ARMv8... There might be a difference between v8/v7 here, do you know?

For v8, this is described in "G1.11.2 Exception priority order" I think:
exceptions taken to EL1 because of configurable access to insns
are item 8, which has higher priority than HCPTR traps (item 10).
This matches the code I have in this patch.

I believe that v7 is the same, and the v7 ARM ARM is just slightly
confusingly worded. The HCPTR documentation says that setting TCPn
to 1 traps "any otherwise-valid Non-secure access to CPn". The
CheckAdvSIMDOrVFPEnabled() pseudocode also clearly checks CPACR
first and HCPTR second.

-- PMM

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