Re: [PATCH 04/15] pcie: Add callback preceding SR-IOV VFs update

[Michael S. Tsirkin]

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.maniak@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