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Mon, 20 Jun 2022 01:48:14 -0700 (PDT) Received: from localhost ([212.145.226.77]) by smtp.gmail.com with ESMTPSA id d6-20020adfef86000000b0021b8d1b0568sm3545680wro.52.2022.06.20.01.48.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jun 2022 01:48:13 -0700 (PDT) From: Juan Quintela To: Leonardo Bras Cc: Daniel P. =?utf-8?Q?Berrang=C3=A9?= , "Dr. David Alan Gilbert" , Eric Blake , Markus Armbruster , Peter Xu , =?utf-8?B?5b6Q6Zev?= , qemu-devel@nongnu.org Subject: Re: [PATCH v4 2/4] QIOChannelSocket: Fix zero-copy send so socket flush works In-Reply-To: <20220620053944.257547-3-leobras@redhat.com> (Leonardo Bras's message of "Mon, 20 Jun 2022 02:39:43 -0300") References: <20220620053944.257547-1-leobras@redhat.com> <20220620053944.257547-3-leobras@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) Date: Mon, 20 Jun 2022 10:48:13 +0200 Message-ID: <878rpr67qq.fsf@secure.mitica> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=170.10.133.124; envelope-from=quintela@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01, T_SPF_HELO_TEMPERROR=0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Leonardo Bras wrote: > Somewhere between v6 and v7 the of the zero-copy-send patchset a crucial > part of the flushing mechanism got missing: incrementing zero_copy_queued. > > Without that, the flushing interface becomes a no-op, and there is no > guarantee the buffer is really sent. > > This can go as bad as causing a corruption in RAM during migration. > > Fixes: 2bc58ffc2926 ("QIOChannelSocket: Implement io_writev zero copy > flag & io_flush for CONFIG_LINUX") > Reported-by: =E5=BE=90=E9=97=AF > Signed-off-by: Leonardo Bras > Reviewed-by: Daniel P. Berrang=C3=A9 Reviewed-by: Juan Quintela