Re: [PATCH v4 03/12] KVM: arm64: guest debug, define API headers

[Alex BennÃe]

Peter Maydell <peter.maydell@xxxxxxxxxx> writes:

> On 15 May 2015 at 16:14, Alex BennÃe <alex.bennee@xxxxxxxxxx> wrote:
>>
>> Mark Rutland <mark.rutland@xxxxxxx> writes:
>>
>>> On Fri, May 15, 2015 at 03:27:06PM +0100, Alex BennÃe wrote:
>>>> +/*
>>>> + * See v8 ARM ARM D7.3: Debug Registers
>>>> + *
>>>> + * The control registers are architecturally defined as 32 bits but are
>>>> + * stored as 64 bit values alongside the value registers. This is done
>>>
>>> Stale comment? They're stored as __u32 below.
>>
>> Gah yes it is.
>>
>>> It's possible that the registers could grow in future as happened in the
>>> case of CLIDR_EL1, so it might be worth treating system registers
>>> generally as u64 values.
>>
>> Really? I mean the existing debug *control* registers have reserved bits
>> 24-31 so there is space for expansion.
>
> Other places in the userspace ABI which deal with sysregs (notably
> ONE_REG) consistently define them all as 64-bit (which makes sense
> anyway since the ISA only provides 64-bit accessors to them).
> "Architecturally 32 bits" only means "top 32 bits reserved".

Fair enough, I can switch it back. The main reason I had them as all 64
bit before was because of the mapping onto the sys_regs context. If
everyone is happy bloating the ABI a little I'm OK with that. It will
make the hyp.S macro a little less ugly for one.

>
> -- PMM

-- 
Alex BennÃe
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/