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Wed, 18 Mar 2020 06:32:11 -0700 (PDT) Subject: Re: [PATCH] hw/scsi/vmw_pvscsi: Remove assertion for kick after reset To: Liran Alon , qemu-devel@nongnu.org References: <20200315132634.113632-1-liran.alon@oracle.com> From: Paolo Bonzini Message-ID: <022d8abd-0bca-1d46-381f-0564a00341a4@redhat.com> Date: Wed, 18 Mar 2020 14:32:08 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200315132634.113632-1-liran.alon@oracle.com> Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 63.128.21.74 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: fam@euphon.net, elazar@vastdata.com, dmitry.fleytman@gmail.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 15/03/20 14:26, Liran Alon wrote: > From: Elazar Leibovich > > When running Ubuntu 3.13.0-65-generic guest, QEMU sometimes crashes > during guest ACPI reset. It crashes on assert(s->rings_info_valid) > in pvscsi_process_io(). > > Analyzing the crash revealed that it happens when userspace issues > a sync during a reboot syscall. > > Below are backtraces we gathered from the guests. > > Guest backtrace when issuing PVSCSI_CMD_ADAPTER_RESET: > pci_device_shutdown > device_shutdown > init_pid_ns > init_pid_ns > kernel_power_off > SYSC_reboot > > Guest backtrace when issuing PVSCSI_REG_OFFSET_KICK_RW_IO: > scsi_done > scsi_dispatch_cmd > blk_add_timer > scsi_request_fn > elv_rb_add > __blk_run_queue > queue_unplugged > blk_flush_plug_list > blk_finish_plug > ext4_writepages > set_next_entity > do_writepages > __filemap_fdatawrite_range > filemap_write_and_wait_range > ext4_sync_file > ext4_sync_file > do_fsync > sys_fsync > > Since QEMU pvscsi should imitate VMware pvscsi device emulation, > we decided to imitate VMware's behavior in this case. > > To check VMware behavior, we wrote a kernel module that issues > a reset to the pvscsi device and then issues a kick. We ran it on > VMware ESXi 6.5 and it seems that it simply ignores the kick. > Hence, we decided to ignore the kick as well. > > Signed-off-by: Elazar Leibovich > Signed-off-by: Liran Alon > --- > hw/scsi/vmw_pvscsi.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/hw/scsi/vmw_pvscsi.c b/hw/scsi/vmw_pvscsi.c > index c91352cf46de..b2bb80449bba 100644 > --- a/hw/scsi/vmw_pvscsi.c > +++ b/hw/scsi/vmw_pvscsi.c > @@ -719,7 +719,12 @@ pvscsi_process_io(PVSCSIState *s) > PVSCSIRingReqDesc descr; > hwaddr next_descr_pa; > > - assert(s->rings_info_valid); > + if (!s->rings_info_valid) { > + qemu_log("WARNING: PVSCSI: Cannot process I/O when " > + "rings are not valid.\n"); > + return; > + } > + > while ((next_descr_pa = pvscsi_ring_pop_req_descr(&s->rings)) != 0) { > > /* Only read after production index verification */ > Queued, with the qemu_log removed even. Paolo