Re: [PATCH] hw/scsi/vmw_pvscsi: Remove assertion for kick after reset

[Paolo Bonzini]

On 15/03/20 14:26, Liran Alon wrote:
> From: Elazar Leibovich <address@hidden>
> 
> 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 <address@hidden>
> Signed-off-by: Liran Alon <address@hidden>
> ---
>  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