Re: [Qemu-devel] [PATCH 12/16] ahci: ncq migration

[John Snow]

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On 06/26/2015 11:48 AM, Stefan Hajnoczi wrote:
> On Mon, Jun 22, 2015 at 08:21:11PM -0400, John Snow wrote:
>> @@ -1555,6 +1573,35 @@ static int ahci_state_post_load(void
>> *opaque, int version_id) return -1; }
>> 
>> +        for (j = 0; j < AHCI_MAX_CMDS; j++) { +
>> ncq_tfs = &ad->ncq_tfs[j]; +            ncq_tfs->drive = ad; + +
>> if (ncq_tfs->used != ncq_tfs->halt) { +                return
>> -1; +            } +            if (!ncq_tfs->halt) { +
>> continue; +            } +            if (!is_ncq(ncq_tfs->cmd))
>> { +                return -1; +            } +            if
>> (ncq_tfs->slot != ncq_tfs->tag) { +                return -1; +
>> } +            if (ncq_tfs->slot > AHCI_MAX_CMDS) { +
>> return -1; +            } +            ncq_tfs->cmdh =
>> &((AHCICmdHdr *)ad->lst)[ncq_tfs->slot];
> 
> Is there a guarantee that ->lst has been mapped?  Maybe pr->cmd & 
> PORT_CMD_START was 0.
> 
> We need to check that the HBA is in a valid state for NCQ
> processing before attempting this.
> 

Slipped my mind, there should be no way to have ncq_tfs->halt set
under normal circumstances except if the engine is started (and lst is
mapped.)

That said, stream corruption is always possible, so I'll add another
validation check.

An "is not null" check here should be sufficient, due to the "if not
halt" continue up above.

Thanks,
- --js
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