Linux Virtualization - May 2011 - [PATCH] arch/tile: add /proc/tile, /proc/sys/tile, and a sysfs cpu attribute

(adding virtualization mailing list)

On Thursday 19 May 2011, Chris Metcalf wrote:
> On 5/19/2011 9:41 AM, Arnd Bergmann wrote:
> >> /proc/tile/hvconfig
> >>   Detailed configuration description of the hypervisor config
> 
> I'm concerned about moving this one out of /proc, since it's just
(copious)
> free text.  An "hvconfig" (hypervisor config) file describes
hypervisor
> driver "dedicated tiles" that run things like network packet or
PCIe
> ingress/egress processing, etc.  In addition it lists hypervisor driver
> options, boot flags for the kernel, etc, all kinds of things -- and you
> can't really guarantee that it will fit on a 4KB page, though in
practice
> it usually does.  The hypervisor reads this file from the boot stream when
> it boots, and then makes it available to Linux not for Linux's use, or
even
> for programmatic userspace use, but just for end users to be able to review
> and verify that the configuration they think they booted is really what
> they got, for customer remote debugging, etc.  The "remote
debugging"
> aspect makes truncation to page size a particularly worrisome idea.
Since it's not the kernel that is imposing the format here, you could
make it a binary sysfs attribute, which works in the same way as
a proc file and does not have the size limitations.
> >> /proc/tile/board
> >>   Information on part numbers, serial numbers, etc., of the
> >>   hardware that the kernel is executing on
> >>
> >> /proc/tile/switch
> >>   The type of control path for the onboard network switch, if any.
> 
> These two report information about the hardware, not the hypervisor.  For
> example:
> 
> # cat /proc/tile/board
> board_part: 402-00002-05
> board_serial: NBS-5002-00012
> chip_serial: P62338.01.110
> chip_revision: A0
> board_revision: 2.2
> board_description: Tilera TILExpressPro-64, TILEPro64 processor (866
MHz-capable), 1 10GbE, 6 1GbE
> # cat /proc/tile/switch
> control: mdio gbe/0
I think it's ok to have it below /sys/hypervisor, because the information
is provided through a hypervisor ABI, even though it describes something
else. This is more like /sys/firmware, but the boundaries between that
and /sys/hypervisor are not clearly defined when running virtualized anyway.
> The chip_serial and chip_revision can certainly hang off
> /sys/devices/system/cpu along with chip_height and chip_width (I've
made
> this change now) but I don't know where the remaining "board"
level
> description could go.  Note that (as you can see in the source) certain
> boards will also include four lines of output with the "mezzanine
board"
> part number, serial number, revision, and description; this particular
> example doesn't have a mezzanine board.  The "switch" info is
broken out
> into a separate file just to make it easier to script some /etc/rc code
> that launches a configurator for the Marvell switch on some of our boards,
> but is conceptually part of the board info.
> 
> >> /proc/tile/hardwall
> >>   Information on the set of currently active hardwalls (note that
> >>   the implementation is already present in
arch/tile/kernel/hardwall.c;
> >>   this change just enables it)
> 
> This one is not a hypervisor-related file.  It just lists information about
> the set of Linux hardwalls currently active.  Again, it's not primarily
> intended for programmatic use, but as a diagnostic tool.
same here, I'd still put it into the hypervisor structure.

	Arnd

On 5/19/2011 11:22 AM, Arnd Bergmann wrote:
> On Thursday 19 May 2011, Chris Metcalf wrote:
>>>> /proc/tile/board
>>>>   Information on part numbers, serial numbers, etc., of the
>>>>   hardware that the kernel is executing on
>>>>
>>>> /proc/tile/switch
>>>>   The type of control path for the onboard network switch, if
any.
>> These two report information about the hardware, not the hypervisor. 
For
>> example:
>>
>> # cat /proc/tile/board
>> board_part: 402-00002-05
>> board_serial: NBS-5002-00012
>> chip_serial: P62338.01.110
>> chip_revision: A0
>> board_revision: 2.2
>> board_description: Tilera TILExpressPro-64, TILEPro64 processor (866
MHz-capable), 1 10GbE, 6 1GbE
>> # cat /proc/tile/switch
>> control: mdio gbe/0
> I think it's ok to have it below /sys/hypervisor, because the
information
> is provided through a hypervisor ABI, even though it describes something
> else. This is more like /sys/firmware, but the boundaries between that
> and /sys/hypervisor are not clearly defined when running virtualized
anyway.
I'll create a /sys/hypervisor/board/ and report the attributes there.
>>>> /proc/tile/hardwall
>>>>   Information on the set of currently active hardwalls (note
that
>>>>   the implementation is already present in
arch/tile/kernel/hardwall.c;
>>>>   this change just enables it)
>> This one is not a hypervisor-related file.  It just lists information
about
>> the set of Linux hardwalls currently active.  Again, it's not
primarily
>> intended for programmatic use, but as a diagnostic tool.
> same here, I'd still put it into the hypervisor structure.
Since /proc/tile/hardwall has no connection to the hypervisor whatsoever,
I'm reluctant to put it under /sys/hypervisor.

Perhaps in this case it would be reasonable to just have the hardwall
subsystem put the file in /proc/driver/hardwall, or even /proc/hardwall? 
Or I could make the /dev/hardwall char device dump out the ASCII text that
we currently get from /proc/hardwall if you read from it, which is a little
weird but not inconceivable.  For example it currently shows things like this:

# cat /proc/tile/hardwall
2x2 1,1 pids: 484 at 2,1 479 at 1,1
2x2 0,3 pids:

In this example "2x2 1,1" is a 2x2 grid of cpus starting at grid (x,y)
position (1,1), with task 484 bound to the cpu at (x,y) position (2,1).

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com

On Thursday 19 May 2011, Arnd Bergmann wrote:
> > 
> > # cat /proc/tile/board
> > board_part: 402-00002-05
> > board_serial: NBS-5002-00012
> > chip_serial: P62338.01.110
> > chip_revision: A0
> > board_revision: 2.2
> > board_description: Tilera TILExpressPro-64, TILEPro64 processor (866
MHz-capable), 1 10GbE, 6 1GbE
> > # cat /proc/tile/switch
> > control: mdio gbe/0
> 
> I think it's ok to have it below /sys/hypervisor, because the
information
> is provided through a hypervisor ABI, even though it describes something
> else. This is more like /sys/firmware, but the boundaries between that
> and /sys/hypervisor are not clearly defined when running virtualized
anyway.
A minor point that I meant to bring up but had not gotten to:

When you do a /sys/hypervisor/ interface, put everything into a subdirectory
under /sys/hypervisor with the name of your hypervisor, to avoid naming
conflicts, e.g.

/sys/hypervisor/tilera-hv/board/board_serial

	Arnd