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Tue, 15 Jun 2021 09:06:43 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwTh+WpgQkTnH7e2tuCXMkOTJQtEXBOHKGdD/wTGjqGCf3mDW9oO0TzEiR7UeAVP0MBFVPPBQ== X-Received: by 2002:a17:907:1c13:: with SMTP id nc19mr272134ejc.168.1623773201577; Tue, 15 Jun 2021 09:06:41 -0700 (PDT) Received: from dresden.str.redhat.com ([2a02:908:1e46:160:b272:8083:d5:bc7d]) by smtp.gmail.com with ESMTPSA id p14sm12309175eds.19.2021.06.15.09.06.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 15 Jun 2021 09:06:41 -0700 (PDT) Subject: Re: [PATCH v3 2/7] scsi-generic: pass max_segments via max_iov field in BlockLimits To: Paolo Bonzini , qemu-devel@nongnu.org References: <20210603133722.218465-1-pbonzini@redhat.com> <20210603133722.218465-3-pbonzini@redhat.com> From: Max Reitz Message-ID: <21c4273a-6a7c-1e88-1fc6-d9b199de92f1@redhat.com> Date: Tue, 15 Jun 2021 18:06:40 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210603133722.218465-3-pbonzini@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Received-SPF: pass client-ip=170.10.133.124; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.197, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.095, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 03.06.21 15:37, Paolo Bonzini wrote: > I/O to a disk via read/write is not limited by the number of segments allowed > by the host adapter; the kernel can split requests if needed, and the limit > imposed by the host adapter can be very low (256k or so) to avoid that SG_IO > returns EINVAL if memory is heavily fragmented. > > Since this value is only interesting for SG_IO-based I/O, do not include > it in the max_transfer and only take it into account when patching the > block limits VPD page in the scsi-generic device. > > Signed-off-by: Paolo Bonzini > --- > block/file-posix.c | 3 +-- > hw/scsi/scsi-generic.c | 6 ++++-- > 2 files changed, 5 insertions(+), 4 deletions(-) Reviewed-by: Max Reitz