Re: [Xen-devel] [RFC PATCH v3 04/10] arm/mem_access: Add short-descriptor pte typedefs

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 15/06/17 20:44, Julien Grall wrote:
> Hi Andrew,
>
> On 06/15/2017 01:03 PM, Andrew Cooper wrote:
>> On 15/06/17 12:05, Sergej Proskurin wrote:
>>> The current implementation does not provide appropriate types for
>>> short-descriptor translation table entries. As such, this commit
>>> adds new
>>> types, which simplify managing the respective translation table
>>> entries.
>>>
>>> Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
>>> ---
>>> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>>> Cc: Julien Grall <julien.grall@xxxxxxx>
>>> ---
>>> v3: Add more short-descriptor related pte typedefs that will be used by
>>>      the following commits.
>>> ---
>>>   xen/include/asm-arm/page.h | 104
>>> +++++++++++++++++++++++++++++++++++++++++++++
>>>   1 file changed, 104 insertions(+)
>>>
>>> diff --git a/xen/include/asm-arm/page.h b/xen/include/asm-arm/page.h
>>> index e2e4b597a5..7a4aa64144 100644
>>> --- a/xen/include/asm-arm/page.h
>>> +++ b/xen/include/asm-arm/page.h
>>> @@ -205,6 +205,110 @@ typedef union {
>>>       lpae_walk_t walk;
>>>   } lpae_t;
>>>   +/*
>>> + *  Comprises bits of the level 1 short-descriptor format representing
>>> + *  a section.
>>> + */
>>> +typedef struct __packed {
>>> +    unsigned int pxn:1;         /* Privileged Execute Never */
>>
>> (I'm not an ARM maintainer, but) can I recommend using bool bitfields
>> for boolean fields like this.
>
> I was not aware it was possible to do boolean fields. I am all for it.

There isn't a good example in xen yet, but
http://xenbits.xen.org/gitweb/?p=xtf.git;a=commitdiff;h=f099211f2ebdadf61ae6416559220d69b788cd2b
is the XTF work I'm basing some imminent Xen improvements on.

~Andrew

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