Re: [Xen-devel] [PATCH VTPM 1/9] Disable -DGNT_DEBUG and -DGNTMAP_DEBUG

[Matthew Fioravante <matthew.fioravante@xxxxxxxxxx>]

The tpm front/back driver maps and unmaps a grant reference everytime it 
sends a message. I'm not sure this is the most efficient design choice 
but that's what the linux tpm driver did so I followed it. I'd like to 
consider redesigning the driver at some point but right now I don't have 
time.
Compare the outputs of vtpmmgrdom below. Whats happening here is a vtpm 
connects to the manager, requests some entropy from the hardware tpm, 
loads its data and then saves its data.
Tpmback:Info Frontend 10/0 connected
INFO[VTPM]: Passthrough: TPM_GetRandom
INFO[VTPM]: Waiting for commands from vTPM's:
INFO[VTPM]: Passthrough: TPM_GetRandom
INFO[VTPM]: Waiting for commands from vTPM's:
INFO[TPM]: TPM_UnBind
INFO[VTPM]: Loaded hash and key for vtpm 
ac0a5b9e-cbe2-4c07-b43b-1d69e46fb839
INFO[VTPM]: Waiting for commands from vTPM's:
INFO[TPM]: TPM_Bind
INFO[VTPM]: Saved hash and key for vtpm ac0a5b9e-cbe2-4c07-b43b-1d69e46fb839
INFO[VTPM]: Waiting for commands from vTPM's:


gntmap_map_grant_refs(map=0x46378, count=1, domids=0x11fd4c [13...], 
domids_stride=0, refs=0x11fd48 [2047...], writable=3)
gntmap_set_max_grants(map=0x46378, count=128)
Tpmback:Info Frontend 13/0 connected
gntmap_map_grant_refs(map=0x46378, count=1, domids=0x10de94 [13...], 
domids_stride=0, refs=0x2006008 [2046...], writable=1)
gntmap_set_max_grants(map=0x46378, count=128)
gntmap_munmap(map=0x46378, start_address=2007000, count=1)
INFO[VTPM]: Passthrough: TPM_GetRandom
gntmap_map_grant_refs(map=0x46378, count=1, domids=0x10dec4 [13...], 
domids_stride=0, refs=0x2006008 [2046...], writable=2)
gntmap_set_max_grants(map=0x46378, count=128)
gntmap_munmap(map=0x46378, start_address=2007000, count=1)
INFO[VTPM]: Waiting for commands from vTPM's:
gntmap_map_grant_refs(map=0x46378, count=1, domids=0x10de94 [13...], 
domids_stride=0, refs=0x2006008 [2046...], writable=1)
gntmap_set_max_grants(map=0x46378, count=128)
gntmap_munmap(map=0x46378, start_address=2007000, count=1)
INFO[VTPM]: Passthrough: TPM_GetRandom
gntmap_map_grant_refs(map=0x46378, count=1, domids=0x10dec4 [13...], 
domids_stride=0, refs=0x2006008 [2046...], writable=2)
gntmap_set_max_grants(map=0x46378, count=128)
gntmap_munmap(map=0x46378, start_address=2007000, count=1)
INFO[VTPM]: Waiting for commands from vTPM's:
gntmap_map_grant_refs(map=0x46378, count=1, domids=0x10de94 [13...], 
domids_stride=0, refs=0x2006008 [2045...], writable=1)
gntmap_set_max_grants(map=0x46378, count=128)
gntmap_munmap(map=0x46378, start_address=2007000, count=1)
INFO[TPM]: TPM_UnBind
INFO[VTPM]: Loaded hash and key for vtpm 
ac0a5b9e-cbe2-4c07-b43b-1d69e46fb839
gntmap_map_grant_refs(map=0x46378, count=1, domids=0x10dec4 [13...], 
domids_stride=0, refs=0x2006008 [2045...], writable=2)
gntmap_set_max_grants(map=0x46378, count=128)
gntmap_munmap(map=0x46378, start_address=2007000, count=1)
INFO[VTPM]: Waiting for commands from vTPM's:
gntmap_map_grant_refs(map=0x46378, count=1, domids=0x10de94 [13...], 
domids_stride=0, refs=0x2006008 [2045...], writable=1)
gntmap_set_max_grants(map=0x46378, count=128)
gntmap_munmap(map=0x46378, start_address=2007000, count=1)
INFO[TPM]: TPM_Bind
INFO[VTPM]: Saved hash and key for vtpm ac0a5b9e-cbe2-4c07-b43b-1d69e46fb839
gntmap_map_grant_refs(map=0x46378, count=1, domids=0x10dec4 [13...], 
domids_stride=0, refs=0x2006008 [2045...], writable=2)
gntmap_set_max_grants(map=0x46378, count=128)
gntmap_munmap(map=0x46378, start_address=2007000, count=1)


I'm perfectly willing to accept that this is just my problem and the tpm 
driver should be fixed. But I also think it makes sense in general  to 
leave debug defines turned off for default builds.

-----Original Message-----
From: Samuel Thibault [mailto:samuel.thibault@xxxxxxxxxxxx] Sent: 
Monday, November 05, 2012 6:35 PM
To: Fioravante, Matthew E.
Cc: Ian.Campbell@xxxxxxxxxx; xen-devel@xxxxxxxxxxxxx
Subject: Re: [PATCH VTPM 1/9] Disable -DGNT_DEBUG and -DGNTMAP_DEBUG

Fioravante, Matthew E., le Fri 02 Nov 2012 09:19:34 -0400, a écrit :
> It happens in my vtpm domains because the drivers often create and release 
> grant references. This patch isn't completely necessary. Do we want to have 
> these debug prints in the default build?
Well, surely -DGNT_DEBUG doesn't produce any output :) We could however 
drop it, since it only adds overhead to check something that is supposed 
to be already working (and which is quite well tested nowadays).
About -DGNTMAP_DEBUG, which message are you getting printed a lot? Are 
you running out of references in gntmap_find_free_entry, or using 
gntmap_map_grant_refs a lot?
Samuel

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