On Tue, Sep 15, 2020 at 09:20:59AM +0300, Ard Biesheuvel wrote:

The documentation of kmap_atomic() states the following:

 * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
 * gives a more generic (and caching) interface. But kmap_atomic can
 * be used in IRQ contexts, so in some (very limited) cases we need
 * it.

so if this is no longer accurate, perhaps we should fix it?

This hasn't been accurate for at least ten years :)

But another reason I tried to avoid kmap_atomic() is that it disables
preemption unconditionally, even on 64-bit architectures where HIGHMEM
is irrelevant. So using kmap_atomic() here means that the bulk of
WireGuard packet encryption runs with preemption disabled, essentially
for legacy reasons.

Agreed.  We should definitely fix that.

Thanks,
-- 
Email: Herbert Xu [off-list ref]
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