Messages in this thread | | | Date | Wed, 25 Jul 2012 22:06:55 +0200 | From | Paolo Bonzini <> | Subject | Re: virtio(-scsi) vs. chained sg_lists (was Re: [PATCH] scsi: virtio-scsi: Fix address translation failure of HighMem pages used by sg list) |
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Il 25/07/2012 21:16, Boaz Harrosh ha scritto: > The picture confused me. It looked like the first element is the virtio_scsi_cmd_req > not an sgilist-element that points to the struct's buffer. > > In that case then yes your plan of making a two-elements fragment that points to the > original scsi-sglist is perfect. All you have to do is that, and all you have to do > at virtio is use the sg_for_each macro and you are done. > > You don't need any sglist allocation or reshaping. And you can easily support > chaining. Looks like order of magnitude more simple then what you do now
It is.
> So what is the problem?
That not all architectures have ARCH_HAS_SG_CHAIN (though all those I care about do). So I need to go through all architectures and make sure they use for_each_sg, or at least to change ARCH_HAS_SG_CHAIN to a Kconfig define so that dependencies can be expressed properly.
> And BTW you won't need that new __sg_set_page API anymore.
Kind of.
sg_init_table(sg, 2); sg_set_buf(sg[0], req, sizeof(req)); sg_chain(sg[1], scsi_out(sc));
is still a little bit worse than
__sg_set_buf(sg[0], req, sizeof(req)); __sg_chain(sg[1], scsi_out(sc));
Paolo
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