[PATCH] powerpc/powernv: make sure the IOV BAR will not exceed limit after shifting
Wei Yang
weiyang at linux.vnet.ibm.com
Thu Feb 5 14:01:47 AEDT 2015
On Wed, Feb 04, 2015 at 02:53:13PM -0600, Bjorn Helgaas wrote:
>On Wed, Feb 04, 2015 at 11:34:09AM +0800, Wei Yang wrote:
>> On Tue, Feb 03, 2015 at 06:19:26PM -0600, Bjorn Helgaas wrote:
>> >On Tue, Feb 03, 2015 at 03:01:43PM +0800, Wei Yang wrote:
>> >> The actual IOV BAR range is determined by the start address and the actual
>> >> size for vf_num VFs BAR. After shifting the IOV BAR, there would be a
>> >> chance the actual end address exceed the limit and overlap with other
>> >> devices.
>> >>
>> >> This patch adds a check to make sure after shifting, the range will not
>> >> overlap with other devices.
>> >
>> >I folded this into the previous patch (the one that adds
>> >pnv_pci_vf_resource_shift()). And I think that needs to be folded together
>> >with the following one ("powerpc/powernv: Allocate VF PE") because this one
>> >references pdn->vf_pes, which is added by "Allocate VF PE".
>> >
>>
>> Yes. Both need this.
>>
>> >> Signed-off-by: Wei Yang <weiyang at linux.vnet.ibm.com>
>> >> ---
>> >> arch/powerpc/platforms/powernv/pci-ioda.c | 53 ++++++++++++++++++++++++++---
>> >> 1 file changed, 48 insertions(+), 5 deletions(-)
>> >>
>> >> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>> >> index 8456ae8..1a1e74b 100644
>> >> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
>> >> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>> >> @@ -854,16 +854,18 @@ static unsigned int pnv_ioda_dma_weight(struct pci_dev *dev)
>> >> }
>> >>
>> >> #ifdef CONFIG_PCI_IOV
>> >> -static void pnv_pci_vf_resource_shift(struct pci_dev *dev, int offset)
>> >> +static int pnv_pci_vf_resource_shift(struct pci_dev *dev, int offset)
>> >> {
>> >> struct pci_dn *pdn = pci_get_pdn(dev);
>> >> int i;
>> >> struct resource *res;
>> >> resource_size_t size;
>> >> + u16 vf_num;
>> >>
>> >> if (!dev->is_physfn)
>> >> - return;
>> >> + return -EINVAL;
>> >>
>> >> + vf_num = pdn->vf_pes;
>> >
>> >I can't actually build this, but I don't think pdn->vf_pes is defined yet.
>> >
>>
>> The pdn->vf_pes is defined in the next patch, it is not defined yet.
>>
>> I thought the incremental patch means a patch on top of the current patch set,
>> so it is defined as the last patch.
>>
>> >> for (i = PCI_IOV_RESOURCES; i <= PCI_IOV_RESOURCE_END; i++) {
>> >> res = &dev->resource[i];
>> >> if (!res->flags || !res->parent)
>> >> @@ -875,11 +877,49 @@ static void pnv_pci_vf_resource_shift(struct pci_dev *dev, int offset)
>> >> dev_info(&dev->dev, " Shifting VF BAR %pR to\n", res);
>> >> size = pci_iov_resource_size(dev, i);
>> >> res->start += size*offset;
>> >> -
>> >> dev_info(&dev->dev, " %pR\n", res);
>> >> +
>> >> + /*
>> >> + * The actual IOV BAR range is determined by the start address
>> >> + * and the actual size for vf_num VFs BAR. The check here is
>> >> + * to make sure after shifting, the range will not overlap
>> >> + * with other device.
>> >> + */
>> >> + if ((res->start + (size * vf_num)) > res->end) {
>> >> + dev_err(&dev->dev, "VF BAR%d: %pR will conflict with"
>> >> + " other device after shift\n");
>> >
>> >sriov_init() sets up "res" with enough space to contain TotalVF copies
>> >of the VF BAR. By the time we get here, that "res" is in the resource
>> >tree, and you should be able to see it in /proc/iomem.
>> >
>> >For example, if TotalVFs is 128 and VF BAR0 is 1MB in size, the
>> >resource size would be 128 * 1MB = 0x800_0000. If the VF BAR0 in the
>> >SR-IOV Capability contains a base address of 0x8000_0000, the resource
>> >would be:
>> >
>> > [mem 0x8000_0000-0x87ff_ffff]
>> >
>> >We have to assume there's another resource starting immediately after
>> >this one, i.e., at 0x8800_0000, and we have to make sure that when we
>> >change this resource and turn on SR-IOV, we don't overlap with it.
>> >
>> >The shifted resource will start at 0x8000_0000 + 1MB * "offset". The
>> >hardware will respond to a range whose size is 1MB * NumVFs (NumVFs
>> >may be smaller than TotalVFs).
>> >
>> >If we enable 16 VFs and shift by 23, we set VF BAR0 to 0x8000_0000 +
>> >1MB * 23 = 0x8170_0000, and the size is 1MB * 16 = 0x100_0000, so the
>> >new resource will be:
>> >
>> > [mem 0x8170_0000-0x826f_ffff]
>> >
>> >That's fine; it doesn't extend past the original end of 0x87ff_ffff.
>> >But if we enable those same 16 VFs with a shift of 120, we set VF BAR0
>> >to 0x8000_0000 + 1MB * 120 = 0x8780_0000, and the size stays the same,
>> >so the new resource will be:
>> >
>> > [mem 0x8780_0000-0x887f_ffff]
>> >
>> >and that's a problem because we have two devices responding at
>> >0x8800_0000.
>> >
>> >Your test of "res->start + (size * vf_num)) > res->end" is not strict
>> >enough to catch this problem.
>> >
>>
>> Yep, you are right.
>>
>> >I think we need something like the patch below. I restructured it so
>> >we don't have to back out any resource changes if we fail.
>> >
>> >This shifting strategy seems to imply that the closer NumVFs is to
>> >TotalVFs, the less flexibility you have to assign PEs, e.g., if NumVFs
>> >== TotalVFs, you wouldn't be able to shift at all. In this example,
>> >you could shift by anything from 0 to 128 - 16 = 112, but if you
>> >wanted NumVFs = 64, you could only shift by 0 to 64. Is that true?
>> >
>> >I think your M64 BAR gets split into 256 segments, regardless of what
>> >TotalVFs is, so if you expanded the resource to 256 * 1MB for this
>> >example, you would be able to shift by up to 256 - NumVFs. Do you
>> >actually do this somewhere?
>> >
>>
>> Yes, after expanding the resource to 256 * 1MB, it is able to shift up to
>> 256 - NumVFs.
>
>Oh, I see where the expansion happens. We started in sriov_init() with:
>
> res->end = res->start + resource_size(res) * total - 1;
>
>where "total" is TotalVFs, and you expand it to the maximum number of PEs
>in pnv_pci_ioda_fixup_iov_resources():
>
> res->end = res->start + size * phb->ioda.total_pe - 1;
>
>in this path:
>
> pcibios_scan_phb
> pci_create_root_bus
> pci_scan_child_bus
> ...
> sriov_init
> res->end = res->start + ... # as above
> ppc_md.pcibios_fixup_sriov # pnv_pci_ioda_fixup_sriov
> pnv_pci_ioda_fixup_sriov(bus)
> list_for_each_entry(dev, &bus->devices, ...)
> if (dev->subordinate)
> pnv_pci_ioda_fixup_sriov(dev->subordinate) # recurse
> pnv_pci_ioda_fixup_iov_resources(dev)
> res->end = res->start + ... # fixup
>
>I think this will be cleaner if you add an arch interface for use by
>sriov_init(), e.g.,
>
> resource_size_t __weak pcibios_iov_size(struct pci_dev *dev, int resno)
> {
> struct resource *res = &dev->resource[resno + PCI_IOV_RESOURCES];
>
> return resource_size(res) * dev->iov->total_VFs;
> }
>
> static int sriov_int(...)
> {
> ...
> res->end = res->start + pcibios_iov_size(dev, i) - 1;
> ...
> }
>
>and powerpc could override this. That way we would set the size once and
>we wouldn't need a fixup pass, which will keep the pcibios_scan_phb() code
>similar to the common path in pci_scan_root_bus().
>
Bjorn,
The idea is a very good one, but when I try to implement it, there is some
issues. The rely on each other.
The "fixup" will go through all the IOV BARs and calculate the number to
expand. This calculation is based on pci_iov_resource_size(), which is just
under initialization at this stage. BTW, the pdev->sriov is not set neither.
And the "fixup" should be just invoked once, while the pcibios_iov_size() will
be called on every IOV BAR.
>> But currently, on my system, I don't see one case really do
>> this.
>>
>> On my system, there is an Emulex card with 4 PFs.
>>
>> 0006:01:00.0 Ethernet controller: Emulex Corporation OneConnect NIC (Lancer) (rev 10)
>> 0006:01:00.1 Ethernet controller: Emulex Corporation OneConnect NIC (Lancer) (rev 10)
>> 0006:01:00.2 Ethernet controller: Emulex Corporation OneConnect NIC (Lancer) (rev 10)
>> 0006:01:00.3 Ethernet controller: Emulex Corporation OneConnect NIC (Lancer) (rev 10)
>>
>> The max VFs for them are 80, 80, 20, 20, with total number of 200 VFs.
>>
>> be2net 0006:01:00.0: Shifting VF BAR [mem 0x3d40 1000 0000 - 0x3d40 10ff ffff 64bit pref] to 256 segs
>> be2net 0006:01:00.0: [mem 0x3d40 1003 0000 - 0x3d40 10ff ffff 64bit pref] 253 segs offset 3
>> PE range [3 - 82]
>> be2net 0006:01:00.1: Shifting VF BAR [mem 0x3d40 1100 0000 - 0x3d40 11ff ffff 64bit pref] to 256 segs
>> be2net 0006:01:00.1: [mem 0x3d40 1153 0000 - 0x3d40 11ff ffff 64bit pref] 173 segs offset 83
>> PE range [83 - 162]
>> be2net 0006:01:00.2: Shifting VF BAR [mem 0x3d40 1200 0000 - 0x3d40 12ff ffff 64bit pref] to 256 segs
>> be2net 0006:01:00.2: [mem 0x3d40 12a3 0000 - 0x3d40 12ff ffff 64bit pref] 93 segs offset 163
>> PE range [163 - 182]
>> be2net 0006:01:00.3: Shifting VF BAR [mem 0x3d40 1300 0000 - 0x3d40 13ff ffff 64bit pref] to 256 segs
>> be2net 0006:01:00.3: [mem 0x3d40 13b7 0000 - 0x3d40 13ff ffff 64bit pref] 73 segs offset 183
>> PE range [183 - 202]
>>
>> After enable the max number of VFs, even the last VF still has 73 number VF
>> BAR size. So this not trigger the limit, but proves the shift offset could be
>> larger than (TotalVFs - NumVFs).
>
>You expanded the overall resource from "TotalVFs * size" to "256 * size".
>So the offset can be larger than "TotalVFs - NumVFs" but it still cannot be
>larger than "256 - NumVFs". The point is that the range claimed by the
>hardware cannot extend past the range we told the resource tree about.
>That's what the "if (res2.end > res->end)" test is checking.
>
>Normally we compute res->end based on TotalVFs. For PHB3, you compute
>res->end based on 256. Either way, we need to make sure we don't program
>the BAR with an address that causes the hardware to respond to addresses
>past res->end.
>
>Bjorn
>
>> >+ /*
>> >+ * The actual IOV BAR range is determined by the start address
>> >+ * and the actual size for vf_num VFs BAR. This check is to
>> >+ * make sure that after shifting, the range will not overlap
>> >+ * with another device.
>> >+ */
>> >+ size = pci_iov_resource_size(dev, i + PCI_IOV_RESOURCES);
>> >+ res2.flags = res->flags;
>> >+ res2.start = res->start + (size * offset);
>> >+ res2.end = res2.start + (size * vf_num) - 1;
>> >+
>> >+ if (res2.end > res->end) {
>> >+ dev_err(&dev->dev, "VF BAR%d: %pR would extend past %pR (trying to enable %d VFs shifted by %d)\n",
>> >+ i, &res2, res, vf_num, offset);
>> >+ return -EBUSY;
>> >+ }
--
Richard Yang
Help you, Help me
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