Re: [Xen-devel] [PATCH v2 04/15] xen/arm: vgic-v3: Correctly handle RAZ/WI registers

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Ian,

On 02/02/15 15:24, Ian Campbell wrote:
> On Thu, 2015-01-29 at 18:25 +0000, Julien Grall wrote:
>> Some of the registers are accessible via multiple size (see 
>> GICD_IPRIORITYR*).
>>
>> Thoses registers are misimplemented when they should be RAZ. Only
> 
> "Those" and "incorrectly implemented".
> 
>> word-access size are currently allowed for them.
>>
>> To avoid further issues, introduce different label following the access-size
>> of the registers:
>>     - read_as_zero_64 and write_ignore_64: Used for registers accessible
>>     via a double-word.
>>     - read_as_zero_32 and write_ignore_32: Used for registers accessible
>>     via a word.
> 
> 5.1.3 suggests there are at least some 64-bit registers where it ought
> to be possible to read the upper and lower halves independently. Don't
> you need to support that?

Only when the system is supporting AArch32. If the system only supports
AArch64, 64-bit registers can only be read via a 64-bit access.

I don't think we actually support AArch32 on the vGICv3 drivers. And we
don't emulate 32-bits access on 64-bit registers.

I will give a look to it.

> BTW, a reference to 5.1.3 in the changelog would be handy.

I will also mention the version of the document as this paragraph
doesn't exists on the previous version.

Regards,

-- 
Julien Grall

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