On 6/24/2014 5:56 PM, Don Dutile wrote:
On 06/23/2014 06:44 PM, Yishai Hadas wrote:
On 6/23/2014 11:12 PM, Don Dutile wrote:
On 06/23/2014 03:09 PM, Bjorn Helgaas wrote:
[+cc linux-pci, Don]
Adding Alex Williamson in case he can add more to this conversation...
On Mon, Jun 23, 2014 at 8:29 AM, Yishai Hadas
<yishaih@xxxxxxxxxxxxxxxxxx> wrote:
Hi Vijay,
Trying to add AER support for Mellanox NIC in SRIOV environment,
while
evaluating/testing encountered a problem which led me to your
patch accepted as part of kernel 3.8, commit ID
"918b4053184c0ca22236e70e299c5343eea35304".
Have some concerns/questions on:
When working in SRIOV environment VFs may be un-attached, having
no driver
assigned to, or may be attached to Virtual machine to work in some
pass-through mode.
Once working in KVM setup there is pci-stub driver which is loaded
in the
HYP/PF for a given attached VF.
huh? 'loaded in the hyp/pf? .... um, loaded in the host, and a VF is
detached from its host driver -- a VF can be used in the host w/o
any virtualization,
i.e., that's how guest VM is driving the VF: as if it was used by a
guest (host) OS directly --
and attached to pci-stub driver, when assigned to a KVM guest in
pre-VFIO days/ways.
If VFIO used, then VF is attached to vfio-pci driver.
I'm using the aer-inject kernel module and its corresponding
aer-inject tool
to simulate an error in the HYP.
In both cases your commit will cause the AER recovery to fail as
there is no
driver assigned to PF's VFs that supports AER, comparing the code
before
your change.
Without VFIO, I believe that's correct. There was no AER-to-VF
support pre-VFIO days.
I believe with the recent VFIO support,
and modifications to KVM, an AER that is associated with an assigned
VF will
force the crash/halt of the KVM guest -- can't depend on a guest VF
driver clearing
the AER in the hyp/host -- guest isn't privileged enough to clear
the error.
So, crashing the guest is the simple option at the moment, to
contain the error.
Alex: do I have that (vfio aer default) correct, or is that still
site-under-construction?
How about the case that the VF is not attached to a KVM guest
and has no driver loaded on host ? in such a case from code review
and some testing the recovery will
fail as there is no AER aware driver here. What is the expected
solution here ?
Well, how can a VF be attributed to an AER if it's not assigned to a
guest, and it doesn't have a driver loaded for it in the host? i.e.,
if it's not configured, it's sitting idle, so how can it generate an AER?
The expectation is really that it will not participate and won't
vote, however in current code looks like it gets a default vote of
PCI_ERS_RESULT_NO_AER_DRIVER and recovery failed, that's exactly my concern.
In case pci_walk_bus() go over both PF & VF which have same BUS
number this may happen, agree ?
if you are injecting an AER attributed to a device that isn't
configured, then you are contriving a non-valid system
condition/state, and I'm not surprised that the AER handler fails.
Maybe it needs an update/patch for the aer-inject case.
The failure happens once I inject the error to its PF which is
configured.
Any special qemu /stuff is needed to activate the VFIO support ?
would like to give it a try for a case that VF is attached.
I see Alex answered this question. VFIO rocks! ... Alex did a great
job with it.
Definitely cleaned up and more cleanly architected a solution that
will lend itself to incremental for
complete reconstruction/duplication for other arches, busses, iommus,
etc. to follow.
Alex - have on my setup QEMU which comes as part of RH 6.5, it uses
the pci-stub driver, looking for a clear way to replace with a newer one
which supports VFIO.
Should I just download from GIT and run configure, make & make
install or there are other required steps to fully replace ? any pointer
to the required steps may help.
How such cases should work ? my expectation was that the PF will
get the
error detected message then will recognize whether
issue is its own or one of its VFs
The AER packet will have the tag of the VF in if it was the source
of the error;
so the PF will never see it; although one could argue it should be
'promoted'
to the PF if PF/VF needs to clear some state it has wrt the VF (the
SRIOV spec is
lacking of info in this space); _but_, VFIO resets the VF (sets FLR
bit) when the
device is deassigned and before re-attachment to the host, so that
should clear out
any state btwn PF & VF ('should' ... famous last words...).
In my test I have used the aer-inject tool simulating an error
to the BUS that both PF/VF are residing on, putting the function
number to be the PF one, looks like both should be called by the aer
driver as part
of the pci_walk_bus(). As mentioned I got a call only on the PF
and recovery failed as of the VF doesn't include an AER aware driver,
once removed the VF recovery succeeded.
I believe that packet should include some info about the source
of the error isn't it ?
yup.
In addition, looking at IXGBE upstream source code at
ixgbe_error_detected() looks like there is some code running on the
PF that checks whether the source was a VF.
Ping the INTEL gang listed in MAINTAINDERS for ixgbe to see what was
tested, intention of this code wrt AER.
Alex Duyck & Greg Rose are the two I've worked with the most on design
issues in the driver, but others @INTEL may be more active in it now.
Thanks, may be helpful.
By the way: when tried to simulate a VF error using its FN got
below error:
"Error: Failed to write, Inappropriate ioctl for device", any
idea about that error ?
details? how did you simulate the error? -- send cmdline used, or code
snippet to inject error, etc.
that (quickly) looks like a sysfs error reply when an operation is not
supported to a file/device under it.
Working with the downloaded aer-inject-0.1 tool, command line was
./aer-inject test/aer1
content of aer1 file is as below:
AER
BUS 33 DEV 0 FN 0 (33 is the decimal value of 21
hex value of PF & VF bus number)
UNCOR_STATUS POISON_TLP
HEADER_LOG 0 1 2 3
I'm really not an AER expert, so help me understand this question of
recognizing whether an error is associated with a PF or a VF.
In terms of hardware, it looks like the device that detects an error
logs some information and sends an Error Message upstream. The Root
Complex receives the message, captures the source ID from the Error
Message, and may generate an interrupt. I expect this source ID can
be either a PF or a VF; there's no requirement that a VF error must be
reported as though it's from the PF, is there?
and work accordingly, in current code
looks like recovery failed as part of "voting" once there is no
AER handler
assigned to the VFs.
The commit you mentioned has to do with PCI_ERS_RESULT_NO_AER_DRIVER.
We use pci_walk_bus() to figure out whether all the devices in a
subtree have a driver. What subtree is involved here? I would expect
the VFs to be siblings of the PF, not children of it, so I'm not sure
where things went wrong.
Well, VFs could be on virtual busses (ARI turned on), so not
necessarily a
sibling to PF ... and then we have the problem in PCI code of not
being able
to traverse these virtual busses (in some cases; not sure if
pci_walk_bus(),
which is going down the tree vs up the tree, has any problems here
w/VFs on
virtual busses).
Can you collect "lspci -vvv" output and maybe add some debug so we can
see exactly where the error is detected and what devices we're looking
at to conclude that one of them doesn't have a driver?
lspci -vvv for both PF & VF is attached, we can see that VF
(21:00.1) has no driver loaded comparing the PF (Kernel driver in
use: mlx4_core).
um, well, the VF doesn't contain an AER cap strucuture, so expecting
AER support for a pci device (VF or PF) w/o an AER cap is
'wishful'.... so, the VF can't generate an AER b/c it doesn't have the
appropriate cap regs for the AER handler to use to report the error &
recover from it.
In case VF doesn't have AER caps we may expect that once there is
an error let its PF that has the AER caps to know about and let it
handle it on behalf of the VF, doesn't it make sense ?
Do you think that without AER caps for the VF it can work properly
under VFIO driver ?
Bjorn
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