Hi Alex,
The kernel am using is stock Ubuntu-Precise (as I mentioned)
3.2.0-29-generic #46.
I debugged deeper in pci_enable_msix() path, and I believe I have tracked
down the source of the different errors I am seeing. The issue I see is that
pci_find_capability() *sometimes* fails to find PCI_CAP_ID_MSIX capability.
I tracked this down to __pci_find_next_cap_ttl() not being able to find the
needed cap and returns 0.
This leads to three different errors I saw:
Case 1: pci_enable_msix() calls pci_msi_check_device(dev, nvec,
PCI_CAP_ID_MSIX), which calls pci_find_capability() and further returns
EINVAL
Case 2: pci_enable_msix() calls pci_msix_table_size(), which calls
pci_find_capability(dev, PCI_CAP_ID_MSIX), which returns 0. As a result,
pci_msix_table_size() returns 0. Then the following code:
nr_entries = pci_msix_table_size(dev);
if (nvec > nr_entries)
return nr_entries;
causes pci_enable_msix() to return 0 to the caller, so now the caller thinks
that pci_enable_msix() succeeded! However, IRQs were not assigned, so
further call to request_threaded_irq() fails.
(This looks like a kernel bug.)
Case 3: pci_enable_msix() calls msix_capability_init(), which calls
pci_find_capability(dev, PCI_CAP_ID_MSIX), which fails and returns pos==0.
So now msix_capability_init() does not check the return value and proceeds
with setting things up, and eventually fails in call to msix_map_region() =>
ioremap_nocache(), which returns NULL. So msix_capability_init() returns
ENOMEM and further pci_enable_msix() returns ENOMEM.
(So this is another kernel bug of not checking return value of
pci_find_capability(dev, PCI_CAP_ID_MSIX).)
So bottom line is that different failures I saw stem from the same issue of
(sometimes) not finding PCI_CAP_ID_MSIX. It always happens on the second
call to KVM_ASSIGN_DEV_IRQ. Why are two calls required? For example, the
below trace shows the first call succeeding and setting up interrupts
properly, and the second call failing:
kernel: [ 4851.332462] kvm-7636: KVM_ASSIGN_DEV_IRQ assigned_dev_id=918
kernel: [ 4851.333553] pci-stub 0000:03:12.6: irq 257 for MSI/MSI-X
kernel: [ 4851.333573] pci-stub 0000:03:12.6: irq 258 for MSI/MSI-X
kernel: [ 4851.333591] pci-stub 0000:03:12.6: irq 259 for MSI/MSI-X
kernel: [ 4851.333600] kvm-7636: assigned_device_enable_host_msix(): call
request_threaded_irq() assigned_dev_id=918 #0: [v=257 e=0]
kernel: [ 4851.333845] kvm-7636: assigned_device_enable_host_msix(): call
request_threaded_irq() assigned_dev_id=918 #1: [v=258 e=1]
kernel: [ 4851.334055] kvm-7636: assigned_device_enable_host_msix(): call
request_threaded_irq() assigned_dev_id=918 #2: [v=259 e=2]
kernel: [ 4851.334241] kvm-7636: KVM_ASSIGN_DEV_IRQ assigned_dev_id=918 OK
kernel: [ 4851.396339] kvm-7636: KVM_ASSIGN_DEV_IRQ assigned_dev_id=918
kernel: [ 4851.396353] kvm-???: pci_find_capability
__pci_find_next_cap(devfn=150 pos=0) dev=0000:03:12.6 returned 0
kernel: [ 4851.412754] kvm-???: msix_map_region ioremap_nocache(0x100000,
nr_entries=2048 PCI_MSIX_ENTRY_SIZE=16 dev=0000:03:12.6 pos=0 NULL
kernel: [ 4851.429672] kvm-???: msix_capability_init
msix_map_region(dev=0000:03:12.6, pos=0 control=32767) failed NULL
kernel: [ 4851.438726] kvm-???: pci_enable_msix(0000:03:12.6)
msix_capability_init failed, err=-12
kernel: [ 4851.465439] kvm-7636: assigned_device_enable_host_msix()
pci_enable_msix() failed assigned_dev_id=918 irq_name=kvm:0000:03:12.6
err=-12
kernel: [ 4851.484072] kvm-7636: assigned_device_enable_host_msix()
assigned_dev_id=918 #0: [v=0 e=0]
kernel: [ 4851.484076] kvm-7636: assigned_device_enable_host_msix()
assigned_dev_id=918 #1: [v=0 e=1]
kernel: [ 4851.484081] kvm-7636: assigned_device_enable_host_msix()
assigned_dev_id=918 #2: [v=0 e=2]
kernel: [ 4851.484086] kvm-7636: KVM_ASSIGN_DEV_IRQ assigned_dev_id=918
r=-12
Do you think the issue is the second KVM call, or the issue is the HW not
reporting the capability sometimes?
Looking at the latest 3.7 kernel code sources, I see that all relevant
functions (pci_enable_msix, pci_find_capability and msix_capability_init)
would behave the same way WRT to pci_find_capability() call. And anyways,
moving to upstream kernel is not an option for me at this point.
Please let me know what do you think the next step would be.
Thanks,
Alex.
-----Original Message-----
From: Alex Williamson
Sent: 10 December, 2012 10:45 PM
To: Alex Lyakas
Cc: kvm@xxxxxxxxxxxxxxx ; linux-pci@xxxxxxxxxxxxxxx ; Yair Hershko ; Shyam
Kaushik
Subject: Re: pci_enable_msix() fails with ENOMEM/EINVAL
On Sat, 2012-12-08 at 14:14 +0200, Alex Lyakas wrote:
Hi Alex,
first of all, I apologize for not reporting things properly. The "vector"
values that I see passed to request_threaded_irq() are not zeros. They are
unique IRQ values as you mentioned. I do not, however, see the
disabling-and-reenabling sequence as you wrote.
The disabling-reenabling is an artifact of the new code to handle
runtime vector updates, which enables CPU affinity of vectors and guests
that behave slightly different, like FreeBSD. This is a good reminder
that you're running an old version of qemu and should probably update to
the latest release for debugging.
The usual sequence for me is
calling KVM_ASSIGN_DEV_IRQ twice for the same assigned_dev-id:
[ 2423.990404] kvm-32353: KVM_ASSIGN_DEV_IRQ assigned_dev_id=946
[ 2423.991585] kvm-32353: assigned_device_enable_host_msix(): call
request_threaded_irq() assigned_dev_id=946 #0: [v=158 e=0]
[ 2423.991810] kvm-32353: assigned_device_enable_host_msix(): call
request_threaded_irq() assigned_dev_id=946 #1: [v=159 e=1]
[ 2423.991869] kvm-32353: assigned_device_enable_host_msix(): call
request_threaded_irq() assigned_dev_id=946 #2: [v=160 e=2]
[ 2424.054320] kvm-32353: KVM_ASSIGN_DEV_IRQ assigned_dev_id=946
[ 2424.055337] kvm-32353: assigned_device_enable_host_msix(): call
request_threaded_irq() assigned_dev_id=946 #0: [v=158 e=0]
[ 2424.055516] kvm-32353: assigned_device_enable_host_msix(): call
request_threaded_irq() assigned_dev_id=946 #1: [v=159 e=1]
[ 2424.055673] kvm-32353: assigned_device_enable_host_msix(): call
request_threaded_irq() assigned_dev_id=946 #2: [v=160 e=2]
As you requested, I specified the intremap=off option to the kernel (saw
that nointremap is deprecated), and reproduced. I had to set the
allow_unsafe_assigned_interrupts parameter of kvm.ko module.
Yep, sorry I forgot to mention that. What kernel are you trying all of
this on? If it's not a recent upstream kernel, please verify on that.
With irqbalance running, I saw that pci_enable_msix() does not report
failure, but does not set up the interrupt verctor, and further call to
request_threaded_irq() fails with EBUSY:
[ 2425.292444] kvm-32353: KVM_ASSIGN_DEV_IRQ assigned_dev_id=913
[ 2425.292458] kvm-32353: assigned_device_enable_host_msix(): call
request_threaded_irq() assigned_dev_id=913 #0: [v=0 e=0]
[ 2425.292753] kvm-32353: assigned_device_enable_host_msix()
request_threaded_irq(vector=0) failed assigned_dev_id=913
irq_name=kvm:0000:03:12.1 err=-16
Dec 6 19:36:04 ubuntu-sata-21 kernel: [ 2425.294434] kvm-32353:
KVM_ASSIGN_DEV_IRQ assigned_dev_id=913 r=-16
Then I turned irqbalance off, and reproduced again; this time
pci_enable_msix() returns EINVAL (-22). I printed out the vector numbers
after pci_enable_msix() failure, and they are all zeros:
[151186.446688] kvm-1923: KVM_ASSIGN_DEV_IRQ assigned_dev_id=918
[151186.446705] kvm-1923: assigned_device_enable_host_msix()
pci_enable_msix() failed assigned_dev_id=918 irq_name=kvm:0000:03:12.6
err=-22
[151186.484409] kvm-1923: assigned_device_enable_host_msix()
assigned_dev_id=918 #0: [v=0 e=0]
[151186.484413] kvm-1923: assigned_device_enable_host_msix()
assigned_dev_id=918 #1: [v=0 e=1]
[151186.484416] kvm-1923: assigned_device_enable_host_msix()
assigned_dev_id=918 #2: [v=0 e=2]
[151186.484419] kvm-1923: KVM_ASSIGN_DEV_IRQ assigned_dev_id=918 r=-22
[151186.522328] kvm-1923: kvm_vm_ioctl_set_msix_nr assigned_dev_id=918
already entries_nr=3
[151186.561093] kvm-1923: kvm_vm_ioctl_set_msix_nr assigned_dev_id=918
r=-22
I attach the full printouts from these two reproductions (kvm-XXX, XXX
being
current->pid).
BTW, these errnos seem pretty random; I think if I try to repro this
again,
I might get different errnos.
Please let me know whether you have any suggestions on how to debug this
further.
So you have two failure modes. In one case pci_enable_msix returns
success and in the other it returns failure, but in both cases the
vectors are all zero. I think the next step is to try to reproduce on
current upstream kernel and qemu. If those still generate similar
failures instrument the pci_enable_msix path to pinpoint where it's
going wrong. Thanks,
Alex
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