Re: [Xen-devel] [PATCH V2 23/33] xen/arm: Allow Xen to run on multiple platform without recompilation

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 05/08/2013 04:35 PM, Ian Campbell wrote:

> On Wed, 2013-05-08 at 16:32 +0100, Ian Campbell wrote:
>>> +/* Helper to read/write a register */
>>> +static inline uint32_t platform_read_register(uint32_t addr)
>>> +{
>>> +    volatile const uint32_t *reg;
>>> +    uint32_t value;
>>> +
>>> +    set_fixmap(FIXMAP_MISC, addr >> PAGE_SHIFT, DEV_SHARED);
>>> +    reg = (uint32_t *)(FIXMAP_ADDR(FIXMAP_MISC) + (addr & ~PAGE_MASK));
>>> +    value = *reg;
>>> +    dsb(); isb();
>>> +    clear_fixmap(FIXMAP_MISC);
>>
>> I don't think the fixmap is per-PCPU so you probably want some locking
>> here.
>>
>> FIXMAP_MISC is a bit of an awful thing, but this isn't especially new,
>> so OK.
> 
> In fact now I'm wondering if the platform specific code shouldn't
> establish its own permanent mapping with ioremap and use that.

I will rework this patch with ioremap

-- 
Julien

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