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[2001:470:26:54b:226:9eff:fe70:80c2]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-30f465f836bsm4447501fa.109.2025.04.10.03.51.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Apr 2025 03:51:03 -0700 (PDT) Received: from home.paul.comp (home.paul.comp [IPv6:0:0:0:0:0:0:0:1]) by home.paul.comp (8.15.2/8.15.2/Debian-22+deb11u3) with ESMTP id 53AAp0sc001656; Thu, 10 Apr 2025 13:51:01 +0300 Received: (from paul@localhost) by home.paul.comp (8.15.2/8.15.2/Submit) id 53AAoxkv001655; Thu, 10 Apr 2025 13:50:59 +0300 Date: Thu, 10 Apr 2025 13:50:58 +0300 From: Paul Fertser To: kalavakunta.hari.prasad@gmail.com Cc: sam@mendozajonas.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, npeacock@meta.com, akozlov@meta.com, hkalavakunta@meta.com Subject: Re: [PATCH net-next v2] net: ncsi: Fix GCPS 64-bit member variables Message-ID: References: <20250410012309.1343-1-kalavakunta.hari.prasad@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250410012309.1343-1-kalavakunta.hari.prasad@gmail.com> Hello Hari, Thank you for the patch, it looks really clean. However I have one more question now. On Wed, Apr 09, 2025 at 06:23:08PM -0700, kalavakunta.hari.prasad@gmail.com wrote: > @@ -290,11 +289,11 @@ struct ncsi_rsp_gcps_pkt { > __be32 tx_1023_frames; /* Tx 512-1023 bytes frames */ > __be32 tx_1522_frames; /* Tx 1024-1522 bytes frames */ > __be32 tx_9022_frames; /* Tx 1523-9022 bytes frames */ > - __be32 rx_valid_bytes; /* Rx valid bytes */ > + __be64 rx_valid_bytes; /* Rx valid bytes */ > __be32 rx_runt_pkts; /* Rx error runt packets */ > __be32 rx_jabber_pkts; /* Rx error jabber packets */ > __be32 checksum; /* Checksum */ > -}; > +} __packed __aligned(4); This made me check the Specification and indeed somehow it happened that they have forgotten to ensure natural alignment for 64-bit fields (at least they cared enough to do it for 32-bit values). [0] is the relevant read. > + ncs->hnc_cnt = be64_to_cpu(rsp->cnt); This means that while it works fine on common BMCs now (since they run in 32-bit mode) the access will be trappped as unaligned on 64-bit Arms which one day will be common (Aspeed AST2700, Nuvoton NPCM8XX). So I guess you should be doing `be64_to_cpup(&rsp->cnt)` there. [0] https://www.catb.org/esr/structure-packing/