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Re: [Qemu-devel] [PATCH 2/2] add tracing of scsi requests


From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH 2/2] add tracing of scsi requests
Date: Fri, 15 Apr 2011 16:22:19 +0200
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On 04/15/2011 04:15 PM, Stefan Hajnoczi wrote:
On Fri, Apr 15, 2011 at 2:24 PM, Paolo Bonzini<address@hidden>  wrote:
+disable scsi_req_parsed(int target, int lun, int tag, int cmd, const char *cmdname, int mode, int 
xfer, uint64_t lba) "target %d lun %d tag %d command %d (%s) dir %d length %d lba 
%"PRIu64""

Tracing strings isn't possible with all trace backends, so we should
avoid it.  It works fine with stderr but other trace backends may not
be in the same address space (they are unable to dereference pointers
to strings) or simply not have the ability to record variable-length
data.

Yeah, I saw them. What happens with the other backends? Do they crash or do they just record bogus data? If the latter (like IIRC simpletrace), I'd really like to keep the string. It is duplicating the cmd argument, so it is possible to work without it on non-stderr backends; with stderr OTOH the human-readable version is really useful before you have learnt the SCSI spec by heart. :)

Paolo



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