From: Alexander Graf
...
> > + page = pfn_to_page(pfn);
> > + eaddr = (unsigned long)kmap_atomic(page);
> > + eaddr |= addr & ~PAGE_MASK;
> > + *instr = *(u32 *)eaddr;
> > + kunmap_atomic((u32 *)eaddr);
>
> I think I'd rather write this as
>
> *instr = *(u32 *)(eaddr | (addr & ~PAGE));
> kunmap_atomic((void*)eaddr);
>
> to make sure we pass the unmap function the same value we got from the
> map function.
>
> Otherwise looks good to me.
Is there any mileage in keeping a virtual address page allocated (per cpu)
for this (and similar) accesses to physical memory?
Not having to search for a free VA page might speed things up (if that matters).
You also probably want the page mapped uncached - no point polluting the data
cache.
David
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