On Tue, Oct 12, 2021 at 03:25:12AM -0400, Michael S. Tsirkin wrote:
> On Thu, Oct 07, 2021 at 06:23:55PM +0200, Lukasz Maniak wrote:
> > PCIe devices implementing SR-IOV may need to perform certain actions
> > before the VFs are unrealized or vice versa.
> >
> > Signed-off-by: Lukasz Maniak <lukasz.man...@linux.intel.com>
>
> Callbacks are annoying and easy to misuse though.
> VFs are enabled through a config cycle, we generally just
> have devices invoke the capability handler.
> E.g.
>
> static void pci_bridge_dev_write_config(PCIDevice *d,
> uint32_t address, uint32_t val, int
> len)
> {
> pci_bridge_write_config(d, address, val, len);
> if (msi_present(d)) {
> msi_write_config(d, address, val, len);
> }
> }
>
> this makes it easy to do whatever you want before/after
> the write. You can also add a helper to check
> that SRIOV is being enabled/disabled if necessary.
>
> > ---
> > docs/pcie_sriov.txt | 2 +-
> > hw/pci/pcie_sriov.c | 14 +++++++++++++-
> > include/hw/pci/pcie_sriov.h | 8 +++++++-
> > 3 files changed, 21 insertions(+), 3 deletions(-)
> >
> > diff --git a/docs/pcie_sriov.txt b/docs/pcie_sriov.txt
> > index f5e891e1d4..63ca1a7b8e 100644
> > --- a/docs/pcie_sriov.txt
> > +++ b/docs/pcie_sriov.txt
> > @@ -57,7 +57,7 @@ setting up a BAR for a VF.
> > /* Add and initialize the SR/IOV capability */
> > pcie_sriov_pf_init(d, 0x200, "your_virtual_dev",
> > vf_devid, initial_vfs, total_vfs,
> > - fun_offset, stride);
> > + fun_offset, stride, pre_vfs_update_cb);
> >
> > /* Set up individual VF BARs (parameters as for normal BARs) */
> > pcie_sriov_pf_init_vf_bar( ... )
> > diff --git a/hw/pci/pcie_sriov.c b/hw/pci/pcie_sriov.c
> > index 501a1ff433..cac2aee061 100644
> > --- a/hw/pci/pcie_sriov.c
> > +++ b/hw/pci/pcie_sriov.c
> > @@ -30,7 +30,8 @@ static void unregister_vfs(PCIDevice *dev);
> > void pcie_sriov_pf_init(PCIDevice *dev, uint16_t offset,
> > const char *vfname, uint16_t vf_dev_id,
> > uint16_t init_vfs, uint16_t total_vfs,
> > - uint16_t vf_offset, uint16_t vf_stride)
> > + uint16_t vf_offset, uint16_t vf_stride,
> > + SriovVfsUpdate pre_vfs_update)
> > {
> > uint8_t *cfg = dev->config + offset;
> > uint8_t *wmask;
> > @@ -41,6 +42,7 @@ void pcie_sriov_pf_init(PCIDevice *dev, uint16_t offset,
> > dev->exp.sriov_pf.num_vfs = 0;
> > dev->exp.sriov_pf.vfname = g_strdup(vfname);
> > dev->exp.sriov_pf.vf = NULL;
> > + dev->exp.sriov_pf.pre_vfs_update = pre_vfs_update;
> >
> > pci_set_word(cfg + PCI_SRIOV_VF_OFFSET, vf_offset);
> > pci_set_word(cfg + PCI_SRIOV_VF_STRIDE, vf_stride);
> > @@ -180,6 +182,11 @@ static void register_vfs(PCIDevice *dev)
> > assert(dev->exp.sriov_pf.vf);
> >
> > trace_sriov_register_vfs(SRIOV_ID(dev), num_vfs);
> > +
> > + if (dev->exp.sriov_pf.pre_vfs_update) {
> > + dev->exp.sriov_pf.pre_vfs_update(dev, dev->exp.sriov_pf.num_vfs,
> > num_vfs);
> > + }
> > +
> > for (i = 0; i < num_vfs; i++) {
> > dev->exp.sriov_pf.vf[i] = register_vf(dev, devfn,
> > dev->exp.sriov_pf.vfname, i);
> > if (!dev->exp.sriov_pf.vf[i]) {
> > @@ -198,6 +205,11 @@ static void unregister_vfs(PCIDevice *dev)
> > uint16_t i;
> >
> > trace_sriov_unregister_vfs(SRIOV_ID(dev), num_vfs);
> > +
> > + if (dev->exp.sriov_pf.pre_vfs_update) {
> > + dev->exp.sriov_pf.pre_vfs_update(dev, dev->exp.sriov_pf.num_vfs,
> > 0);
> > + }
> > +
> > for (i = 0; i < num_vfs; i++) {
> > PCIDevice *vf = dev->exp.sriov_pf.vf[i];
> > object_property_set_bool(OBJECT(vf), "realized", false,
> > &local_err);
> > diff --git a/include/hw/pci/pcie_sriov.h b/include/hw/pci/pcie_sriov.h
> > index 0974f00054..9ab48b79c0 100644
> > --- a/include/hw/pci/pcie_sriov.h
> > +++ b/include/hw/pci/pcie_sriov.h
> > @@ -13,11 +13,16 @@
> > #ifndef QEMU_PCIE_SRIOV_H
> > #define QEMU_PCIE_SRIOV_H
> >
> > +typedef void (*SriovVfsUpdate)(PCIDevice *dev, uint16_t prev_num_vfs,
> > + uint16_t num_vfs);
> > +
> > struct PCIESriovPF {
> > uint16_t num_vfs; /* Number of virtual functions created */
> > uint8_t vf_bar_type[PCI_NUM_REGIONS]; /* Store type for each VF bar */
> > const char *vfname; /* Reference to the device type used for
> > the VFs */
> > PCIDevice **vf; /* Pointer to an array of num_vfs VF
> > devices */
> > +
> > + SriovVfsUpdate pre_vfs_update; /* Callback preceding VFs count change
> > */
> > };
> >
> > struct PCIESriovVF {
> > @@ -28,7 +33,8 @@ struct PCIESriovVF {
> > void pcie_sriov_pf_init(PCIDevice *dev, uint16_t offset,
> > const char *vfname, uint16_t vf_dev_id,
> > uint16_t init_vfs, uint16_t total_vfs,
> > - uint16_t vf_offset, uint16_t vf_stride);
> > + uint16_t vf_offset, uint16_t vf_stride,
> > + SriovVfsUpdate pre_vfs_update);
> > void pcie_sriov_pf_exit(PCIDevice *dev);
> >
> > /* Set up a VF bar in the SR/IOV bar area */
> > --
> > 2.25.1
>
Hi Michael,
A custom config_write callback was the first approach we used.
However, once implemented, we realized it looks the same as the
pcie_sriov_config_write function. To avoid code duplication and
interfering with the internal SR-IOV structures for purposes of NVMe,
we opted for this callback prior to the VFs update.
After all, we have callbacks in both approaches, config_write and the
added pre_vfs_update, so both are prone to misuse.
But I agree it may not be a good moment yet to add a new API
specifically for SR-IOV functionality, as NVMe will be the first device
to use it.
CCing Knut, perhaps as the author of SR-IOV you have some thoughts on
how the device notification of an upcoming VFs update would be handled.
Thanks,
Lukasz
