When sf_buf_alloc() replaces a virtual-to-physical mapping, it needn't invalidate the TLB(s) if the old mapping wasn't used by the CPU.  With network interfaces that implement checksum off-loading, the old mapping is almost never used by the CPU, only by the device driver for setting up the DMA operation.
When sf_buf_alloc() replaces a virtual-to-physical mapping, it needn't
invalidate the TLB(s) if the old mapping wasn't used by the CPU.  With
network interfaces that implement checksum off-loading, the old mapping is
almost never used by the CPU, only by the device driver for setting up the
DMA operation.

Reviewed by: tegge@

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