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[95.239.64.30]) by smtp.gmail.com with ESMTPSA id t26sm14439420eji.22.2020.12.07.20.50.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Dec 2020 20:50:59 -0800 (PST) Date: Tue, 8 Dec 2020 05:50:50 +0100 From: Andrea Parri To: Michael Kelley Cc: "linux-kernel@vger.kernel.org" , KY Srinivasan , Haiyang Zhang , Stephen Hemminger , Wei Liu , "linux-hyperv@vger.kernel.org" , Andres Beltran , Saruhan Karademir , Juan Vazquez , "David S. Miller" , Jakub Kicinski , "James E.J. Bottomley" , "Martin K. Petersen" , "netdev@vger.kernel.org" , "linux-scsi@vger.kernel.org" Subject: Re: [PATCH v2] Drivers: hv: vmbus: Copy packets sent by Hyper-V out of the ring buffer Message-ID: <20201208045050.GA9609@andrea> References: <20201109100727.9207-1-parri.andrea@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > @@ -419,17 +446,52 @@ static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi) > > struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel) > > { > > struct hv_ring_buffer_info *rbi = &channel->inbound; > > - struct vmpacket_descriptor *desc; > > + struct vmpacket_descriptor *desc, *desc_copy; > > + u32 bytes_avail, pkt_len, pkt_offset; > > > > - hv_debug_delay_test(channel, MESSAGE_DELAY); > > - if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor)) > > + desc = hv_pkt_iter_first_raw(channel); > > + if (!desc) > > return NULL; > > > > - desc = hv_get_ring_buffer(rbi) + rbi->priv_read_index; > > - if (desc) > > - prefetch((char *)desc + (desc->len8 << 3)); > > + bytes_avail = hv_pkt_iter_avail(rbi); > > + > > + /* > > + * Ensure the compiler does not use references to incoming Hyper-V values (which > > + * could change at any moment) when reading local variables later in the code > > + */ > > + pkt_len = READ_ONCE(desc->len8) << 3; > > + pkt_offset = READ_ONCE(desc->offset8) << 3; > > + > > + /* > > + * If pkt_len is invalid, set it to the smaller of hv_pkt_iter_avail() and > > + * rbi->pkt_buffer_size > > + */ > > + if (rbi->pkt_buffer_size < bytes_avail) > > + bytes_avail = rbi->pkt_buffer_size; > > I think the above could be combined with the earlier call to hv_pkt_iter_avail(), > and more logically expressed as: > > bytes_avail = min(rbi->pkt_buffer_size, hv_pkt_iter_avail(rbi)); > > > This is a minor nit. Everything else in this patch looks good to me. Thanks for the feedback, Michael; I'll send v3 to address it shortly. Andrea