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Date: Thu, 1 Mar 2018 21:32:02 +0000
From: "Raslan, KarimAllah" <karahmed@...zon.de>
To: "helgaas@...nel.org" <helgaas@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"bhelgaas@...gle.com" <bhelgaas@...gle.com>
Subject: Re: [PATCH v2] pci: Store more data about VFs into the SRIOV struct
On Thu, 2018-03-01 at 13:34 -0600, Bjorn Helgaas wrote:
> s|pci: Store|PCI/IOV: Store|
>
> (run "git log --oneline drivers/pci/probe.c" to see why)
>
> On Thu, Mar 01, 2018 at 02:26:04PM +0100, KarimAllah Ahmed wrote:
> >
> > ... to avoid reading them from the config space of all the PCI VFs. This is
> > specially a useful optimization when bringing up thousands of VFs.
>
> Please make the changelog complete in itself, so it doesn't have to be
> read in conjunction with the subject. It's OK if you have to repeat
> the subject in the changelog.
ack.
>
> >
> > Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> > Cc: linux-pci@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Signed-off-by: KarimAllah Ahmed <karahmed@...zon.de>
> > ---
> > v1 -> v2:
> > * Rebase on latest + remove dependency on a non-upstream patch.
> >
> > drivers/pci/iov.c | 16 ++++++++++++++++
> > drivers/pci/pci.h | 5 +++++
> > drivers/pci/probe.c | 42 ++++++++++++++++++++++++++++++++----------
> > 3 files changed, 53 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> > index 677924a..e1d2e3f 100644
> > --- a/drivers/pci/iov.c
> > +++ b/drivers/pci/iov.c
> > @@ -114,6 +114,19 @@ resource_size_t pci_iov_resource_size(struct pci_dev *dev, int resno)
> > return dev->sriov->barsz[resno - PCI_IOV_RESOURCES];
> > }
> >
> > +static void pci_read_vf_config_common(struct pci_bus *bus, struct pci_dev *dev)
> > +{
> > + int devfn = pci_iov_virtfn_devfn(dev, 0);
> > +
> > + pci_bus_read_config_dword(bus, devfn, PCI_CLASS_REVISION,
> > + &dev->sriov->class);
> > + pci_bus_read_config_word(bus, devfn, PCI_SUBSYSTEM_ID,
> > + &dev->sriov->subsystem_device);
> > + pci_bus_read_config_word(bus, devfn, PCI_SUBSYSTEM_VENDOR_ID,
> > + &dev->sriov->subsystem_vendor);
> > + pci_bus_read_config_byte(bus, devfn, PCI_HEADER_TYPE, &dev->sriov->hdr_type);
>
> Can't you do this a little later, e.g., after pci_iov_add_virtfn()
> calls pci_setup_device(), and then use the standard
> pci_read_config_*() interfaces instead of the special
> pci_bus_read_config*() ones?
ack.
I moved it after "pci_iov_virtfn_devfn".
>
> >
> > +}
> > +
> > int pci_iov_add_virtfn(struct pci_dev *dev, int id)
> > {
> > int i;
> > @@ -133,6 +146,9 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
> > if (!virtfn)
> > goto failed0;
> >
> > + if (id == 0)
> > + pci_read_vf_config_common(bus, dev);
> > +
> > virtfn->devfn = pci_iov_virtfn_devfn(dev, id);
> > virtfn->vendor = dev->vendor;
> > virtfn->device = iov->vf_device;
> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> > index fcd8191..346daa5 100644
> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -271,6 +271,11 @@ struct pci_sriov {
> > u16 driver_max_VFs; /* Max num VFs driver supports */
> > struct pci_dev *dev; /* Lowest numbered PF */
> > struct pci_dev *self; /* This PF */
> > + u8 hdr_type; /* VF header type */
> > + u32 class; /* VF device */
> > + u16 device; /* VF device */
> > + u16 subsystem_vendor; /* VF subsystem vendor */
> > + u16 subsystem_device; /* VF subsystem device */
>
> Please make the whitespace here match the existing code, i.e.,
> line up the structure element names and comments.
ack!
>
> >
> > resource_size_t barsz[PCI_SRIOV_NUM_BARS]; /* VF BAR size */
> > bool drivers_autoprobe; /* Auto probing of VFs by driver */
> > };
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index ef53774..aeaa10a 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -180,6 +180,7 @@ static inline unsigned long decode_bar(struct pci_dev *dev, u32 bar)
> > int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
> > struct resource *res, unsigned int pos)
> > {
> > + int bar = res - dev->resource;
> > u32 l = 0, sz = 0, mask;
> > u64 l64, sz64, mask64;
> > u16 orig_cmd;
> > @@ -199,9 +200,13 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
> > res->name = pci_name(dev);
> >
> > pci_read_config_dword(dev, pos, &l);
> > - pci_write_config_dword(dev, pos, l | mask);
> > - pci_read_config_dword(dev, pos, &sz);
> > - pci_write_config_dword(dev, pos, l);
> > + if (dev->is_virtfn) {
> > + sz = dev->physfn->sriov->barsz[bar] & 0xffffffff;
> > + } else {
> > + pci_write_config_dword(dev, pos, l | mask);
> > + pci_read_config_dword(dev, pos, &sz);
> > + pci_write_config_dword(dev, pos, l);
> > + }
>
> This part is not like the others, i.e., the others are caching info
> from VF 0 in newly-added elements of struct pci_sriov. This also uses
> information from struct pci_sriov, but it's qualitatively different,
> so it should be in a separate patch.
ack. Moved to a seperate patch.
>
> >
> > /*
> > * All bits set in sz means the device isn't working properly.
> > @@ -241,9 +246,14 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
> >
> > if (res->flags & IORESOURCE_MEM_64) {
> > pci_read_config_dword(dev, pos + 4, &l);
> > - pci_write_config_dword(dev, pos + 4, ~0);
> > - pci_read_config_dword(dev, pos + 4, &sz);
> > - pci_write_config_dword(dev, pos + 4, l);
> > +
> > + if (dev->is_virtfn) {
> > + sz = (dev->physfn->sriov->barsz[bar] >> 32) & 0xffffffff;
> > + } else {
> > + pci_write_config_dword(dev, pos + 4, ~0);
> > + pci_read_config_dword(dev, pos + 4, &sz);
> > + pci_write_config_dword(dev, pos + 4, l);
> > + }
> >
> > l64 |= ((u64)l << 32);
> > sz64 |= ((u64)sz << 32);
> > @@ -332,6 +342,8 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
> > for (pos = 0; pos < howmany; pos++) {
> > struct resource *res = &dev->resource[pos];
> > reg = PCI_BASE_ADDRESS_0 + (pos << 2);
> > + if (dev->is_virtfn && dev->physfn->sriov->barsz[pos] == 0)
> > + continue;
> > pos += __pci_read_base(dev, pci_bar_unknown, res, reg);
> > }
> >
> > @@ -1454,7 +1466,9 @@ int pci_setup_device(struct pci_dev *dev)
> > struct pci_bus_region region;
> > struct resource *res;
> >
> > - if (pci_read_config_byte(dev, PCI_HEADER_TYPE, &hdr_type))
> > + if (dev->is_virtfn)
> > + hdr_type = dev->physfn->sriov->hdr_type;
> > + else if (pci_read_config_byte(dev, PCI_HEADER_TYPE, &hdr_type))
> > return -EIO;
> >
> > dev->sysdata = dev->bus->sysdata;
> > @@ -1477,7 +1491,10 @@ int pci_setup_device(struct pci_dev *dev)
> > dev->bus->number, PCI_SLOT(dev->devfn),
> > PCI_FUNC(dev->devfn));
> >
> > - pci_read_config_dword(dev, PCI_CLASS_REVISION, &class);
> > + if (dev->is_virtfn)
> > + class = dev->physfn->sriov->class;
> > + else
> > + pci_read_config_dword(dev, PCI_CLASS_REVISION, &class);
> > dev->revision = class & 0xff;
> > dev->class = class >> 8; /* upper 3 bytes */
> >
> > @@ -1517,8 +1534,13 @@ int pci_setup_device(struct pci_dev *dev)
> > goto bad;
> > pci_read_irq(dev);
> > pci_read_bases(dev, 6, PCI_ROM_ADDRESS);
> > - pci_read_config_word(dev, PCI_SUBSYSTEM_VENDOR_ID, &dev->subsystem_vendor);
> > - pci_read_config_word(dev, PCI_SUBSYSTEM_ID, &dev->subsystem_device);
> > + if (dev->is_virtfn) {
> > + dev->subsystem_vendor = dev->physfn->sriov->subsystem_vendor;
> > + dev->subsystem_device = dev->physfn->sriov->subsystem_device;
>
> PCIe r4.0, sec 9.3.4.1.13 requires that Subsystem Vendor ID be the
> same for the PF and all VFs, but sec 9.3.4.1.14 says the PF and VF may
> have different Subsystem IDs. I know you're caching the Subsystem ID
> from VF 0, not the PF, but I don't see anything that requires all the
> VFs to have the same Subsystem ID.
>
> I think the same is technically true for the Revision ID. It might be
> reasonable to assume all the VFs have the same values, but maybe worth
> a comment.
I added a comment about that for the 3 fields.
>
> >
> > + } else {
> > + pci_read_config_word(dev, PCI_SUBSYSTEM_VENDOR_ID, &dev->subsystem_vendor);
> > + pci_read_config_word(dev, PCI_SUBSYSTEM_ID, &dev->subsystem_device);
> > + }
> >
> > /*
> > * Do the ugly legacy mode stuff here rather than broken chip
> > --
> > 2.7.4
> >
>
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