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Re: [Xen-devel] [PATCH 04/10] xen/arm: vgic-v3: Don't check the size when we ignore the write/read as zero

On 20/01/15 17:41, Julien Grall wrote:
> Hi Ian,
> On 20/01/15 15:57, Ian Campbell wrote:
>> On Mon, 2015-01-19 at 16:29 +0000, Julien Grall wrote:
>>> In general, it's not necessary/important to check the size.
>> Only if the docs say this register can be accessed by a partial
>> read/write, or if it is implementation defined what the result would be
>> (and RAZ/WI is within the set of allowable actions).
>> Do you have a reference for the behaviour of GICR accesses which aren't
>> of the register's natural size?
> It's clearly specify in the spec if the register can be accessed with a
> non-natural size.
> AFAICT, the spec doesn't give a specific behavior if the register
> doesn't support byte/word/double word access.

Hmmm, I read quickly the spec. 5.1.3 says: "Accessing any of these
registers using other accesses is UNPREDICTABLE".

So I think it's fine to go on this behavior. It would help to have a
simpler code.


Julien Grall

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