Re: [Qemu-devel] [PATCH 2/2] ipmi: Use proper struct reference for BT vmstate

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* minyard@acm.org (minyard@acm.org) wrote:
> From: Corey Minyard <cminyard@mvista.com>
> 
> The vmstate for isa_ipmi_bt was referencing into the bt structure,
> instead create a bt structure separate and use that.
> 
> The version 1 of the BT transfer was fairly broken, if a migration
> occured during an IPMI operation, it is likely the migration would
> be corrupted because I misunderstood the VMSTATE_VBUFFER_UINT32()
> handling, I thought it handled transferring the length field,
> too.  So I just remove support for that.  I doubt anyone is using
> it at this point.
> 
> This also removes the transfer of use_irq, since that should come
> from configuration.
> 
> Signed-off-by: Corey Minyard <cminyard@mvista.com>
> ---
>  hw/ipmi/isa_ipmi_bt.c | 43 ++++++++++++++++++++++++++++++-------------
>  1 file changed, 30 insertions(+), 13 deletions(-)
> 
> diff --git a/hw/ipmi/isa_ipmi_bt.c b/hw/ipmi/isa_ipmi_bt.c
> index e946030..a990ab7 100644
> --- a/hw/ipmi/isa_ipmi_bt.c
> +++ b/hw/ipmi/isa_ipmi_bt.c
> @@ -450,22 +450,39 @@ static void isa_ipmi_bt_realize(DeviceState *dev, Error **errp)
>      isa_register_ioport(isadev, &iib->bt.io, iib->bt.io_base);
>  }
>  
> -static const VMStateDescription vmstate_ISAIPMIBTDevice = {
> -    .name = TYPE_IPMI_INTERFACE,
> +
> +const VMStateDescription vmstate_IPMIBT = {
> +    .name = TYPE_IPMI_INTERFACE_PREFIX "bt",
>      .version_id = 1,
>      .minimum_version_id = 1,
>      .fields      = (VMStateField[]) {
> -        VMSTATE_BOOL(bt.obf_irq_set, ISAIPMIBTDevice),
> -        VMSTATE_BOOL(bt.atn_irq_set, ISAIPMIBTDevice),
> -        VMSTATE_BOOL(bt.use_irq, ISAIPMIBTDevice),
> -        VMSTATE_BOOL(bt.irqs_enabled, ISAIPMIBTDevice),
> -        VMSTATE_UINT32(bt.outpos, ISAIPMIBTDevice),
> -        VMSTATE_VBUFFER_UINT32(bt.outmsg, ISAIPMIBTDevice, 1, NULL, bt.outlen),
> -        VMSTATE_VBUFFER_UINT32(bt.inmsg, ISAIPMIBTDevice, 1, NULL, bt.inlen),
> -        VMSTATE_UINT8(bt.control_reg, ISAIPMIBTDevice),
> -        VMSTATE_UINT8(bt.mask_reg, ISAIPMIBTDevice),
> -        VMSTATE_UINT8(bt.waiting_rsp, ISAIPMIBTDevice),
> -        VMSTATE_UINT8(bt.waiting_seq, ISAIPMIBTDevice),
> +        VMSTATE_BOOL(obf_irq_set, IPMIBT),
> +        VMSTATE_BOOL(atn_irq_set, IPMIBT),
> +        VMSTATE_BOOL(irqs_enabled, IPMIBT),
> +        VMSTATE_UINT32(outpos, IPMIBT),
> +        VMSTATE_UINT32(outlen, IPMIBT),
> +        VMSTATE_UINT8_ARRAY(outmsg, IPMIBT, MAX_IPMI_MSG_SIZE),
> +        VMSTATE_UINT32(inlen, IPMIBT),
> +        VMSTATE_UINT8_ARRAY(inmsg, IPMIBT, MAX_IPMI_MSG_SIZE),
> +        VMSTATE_UINT8(control_reg, IPMIBT),
> +        VMSTATE_UINT8(mask_reg, IPMIBT),
> +        VMSTATE_UINT8(waiting_rsp, IPMIBT),
> +        VMSTATE_UINT8(waiting_seq, IPMIBT),

OK, without knowing anything about the internals of the IPMI model, this
looks simpler; and yes, vbuffer isn't very smart.

You should probably consider either a postload to verify the data,
or be a bit paranoid in the uses.  For example, imagine that 'outpos'
and 'outlen' were for some reason completely bogus huge values and then
you got to ipmi_bt_ioport_read case 1, I think you could read off the
end of outmsg.

Dave

> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static const VMStateDescription vmstate_ISAIPMIBTDevice = {
> +    .name = TYPE_IPMI_INTERFACE_PREFIX "isa-bt",
> +    .version_id = 2,
> +    .minimum_version_id = 2,
> +    /*
> +     * Version 1 had messed up the array transfer, it's not even usable
> +     * because it used VMSTATE_VBUFFER_UINT32, but it did not transfer
> +     * the buffer length, so random things would happen.
> +     */
> +    .fields      = (VMStateField[]) {
> +        VMSTATE_STRUCT(bt, ISAIPMIBTDevice, 1, vmstate_IPMIBT, IPMIBT),
>          VMSTATE_END_OF_LIST()
>      }
>  };
> -- 
> 2.7.4
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK