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[79.55.110.244]) by smtp.gmail.com with ESMTPSA id x10-20020a05600c21ca00b003a6125562e1sm5057622wmj.46.2022.11.25.07.34.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Nov 2022 07:34:36 -0800 (PST) From: "Fabio M. De Francesco" To: netdev@vger.kernel.org, Anirudh Venkataramanan Cc: Ira Weiny , Anirudh Venkataramanan , Ayush Sawal Subject: Re: [PATCH v2 net-next 1/6] ch_ktls: Use memcpy_from_page() instead of k[un]map_atomic() Date: Fri, 25 Nov 2022 16:34:35 +0100 Message-ID: <5779845.MhkbZ0Pkbq@suse> In-Reply-To: <20221123205219.31748-2-anirudh.venkataramanan@intel.com> References: <20221123205219.31748-1-anirudh.venkataramanan@intel.com> <20221123205219.31748-2-anirudh.venkataramanan@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On mercoled=EC 23 novembre 2022 21:52:14 CET Anirudh Venkataramanan wrote: > kmap_atomic() is being deprecated in favor of kmap_local_page(). Replace > the map-memcpy-unmap usage pattern (done using k[un]map_atomic()) with > memcpy_from_page(), which internally uses kmap_local_page() and > kunmap_local(). This renders the variables 'data' and 'vaddr' unnecessary, > and so remove these too. >=20 > Note that kmap_atomic() disables preemption and page-fault processing, but > kmap_local_page() doesn't. When converting uses of kmap_atomic(), one has > to check if the code being executed between the map/unmap implicitly > depends on page-faults and/or preemption being disabled. If yes, then code > to disable page-faults and/or preemption should also be added for > functional correctness. That however doesn't appear to be the case here, > so just memcpy_from_page() is used. Just two marginal notes: It looks like you are explaining your mental process and teaching how =20 developers should approach these kinds of conversions. Although I'm OK with= =20 this exposition, a plain assurance that the code being executed between the= =20 map / unmap did not depend on page-faults and/or preemption being disabled= =20 would have sufficed. :-) Ira were suggesting to not use "it appears" and replace with stronger and=20 clearer assertions like "it is" or "I can confirm that" (or whatever else l= ike =20 these). As said, no problems at all with regard to the overall goodness of this and= =20 the other patches. >=20 > Also note that the page being mapped is not allocated by the driver, and = so > the driver doesn't know if the page is in normal memory. This is the reas= on > kmap_local_page() is used (via memcpy_from_page()) as opposed to > page_address(). >=20 > I don't have hardware, so this change has only been compile tested. >=20 > Cc: Ayush Sawal > Cc: Ira Weiny > Cc: Fabio M. De Francesco > Suggested-by: Fabio M. De Francesco > Signed-off-by: Anirudh Venkataramanan > --- > v1 -> v2: > Use memcpy_from_page() as suggested by Fabio > Add a "Suggested-by" tag > Rework commit message > Some emails cc'd in v1 are defunct. Drop them. The MAINTAINERS file for > Chelsio drivers likely needs an update > --- > .../chelsio/inline_crypto/ch_ktls/chcr_ktls.c | 26 +++++++++---------- > 1 file changed, 12 insertions(+), 14 deletions(-) It looks good to me. Reviewed-by: Fabio M. De Francesco Thanks, =46abio > diff --git a/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls= =2Ec > b/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c index > da9973b..1a5fdd7 100644 > --- a/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c > +++ b/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c > @@ -1839,9 +1839,7 @@ static int chcr_short_record_handler(struct > chcr_ktls_info *tx_info, */ > if (prior_data_len) { > int i =3D 0; > - u8 *data =3D NULL; > skb_frag_t *f; > - u8 *vaddr; > int frag_size =3D 0, frag_delta =3D 0; >=20 > while (remaining > 0) { > @@ -1853,24 +1851,24 @@ static int chcr_short_record_handler(struct > chcr_ktls_info *tx_info, i++; > } > f =3D &record->frags[i]; > - vaddr =3D kmap_atomic(skb_frag_page(f)); > - > - data =3D vaddr + skb_frag_off(f) + remaining; > frag_delta =3D skb_frag_size(f) - remaining; >=20 > if (frag_delta >=3D prior_data_len) { > - memcpy(prior_data, data,=20 prior_data_len); > - kunmap_atomic(vaddr); > + memcpy_from_page(prior_data,=20 skb_frag_page(f), > + skb_frag_off(f) +=20 remaining, > + prior_data_len); > } else { > - memcpy(prior_data, data, frag_delta); > - kunmap_atomic(vaddr); > + memcpy_from_page(prior_data,=20 skb_frag_page(f), > + skb_frag_off(f) +=20 remaining, > + frag_delta); > + > /* get the next page */ > f =3D &record->frags[i + 1]; > - vaddr =3D kmap_atomic(skb_frag_page(f)); > - data =3D vaddr + skb_frag_off(f); > - memcpy(prior_data + frag_delta, > - data, (prior_data_len -=20 frag_delta)); > - kunmap_atomic(vaddr); > + > + memcpy_from_page(prior_data +=20 frag_delta, > + skb_frag_page(f), > + skb_frag_off(f), > + prior_data_len -=20 frag_delta); > } > /* reset tcp_seq as per the prior_data_required=20 len */ > tcp_seq -=3D prior_data_len; > -- > 2.37.2