Re: [PATCH v6 1/6] PCI/IOV: Restore VF resizable BAR state after reset

[Ilpo Järvinen]

On Wed, 26 Mar 2025, Ilpo Järvinen wrote:

> On Thu, 20 Mar 2025, Michał Winiarski wrote:
> 
> > Similar to regular resizable BAR, VF BAR can also be resized, e.g. by
> > the system firmware or the PCI subsystem itself.
> > 
> > Add the capability ID and restore it as a part of IOV state.
> >
> > See PCIe r4.0, sec 9.3.7.4.
> 
> Usually it's best o refer to latest gen doc, the section number seems to 
> be the same also in r6.2.

Actually, it isn't. r6.2 9.3.7 does specify capability IDs so I though you 
be refering to that section, but there's no 9.3.7.4 section at all.

--
 i.

> This didn't refer to spec section that specified VF Rebar ext capability
> (7.8.7) though. I think it should and it would also be good to mention the 
> capability layout is the same as with the rebar cap.
> 
> > Signed-off-by: Michał Winiarski <michal.winiarski@xxxxxxxxx>
> > Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> > Reviewed-by: Christian König <christian.koenig@xxxxxxx>
> > ---
> >  drivers/pci/iov.c             | 30 +++++++++++++++++++++++++++++-
> >  drivers/pci/pci.h             |  1 +
> >  include/uapi/linux/pci_regs.h |  1 +
> >  3 files changed, 31 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> > index 121540f57d4bf..bf95387993cd5 100644
> > --- a/drivers/pci/iov.c
> > +++ b/drivers/pci/iov.c
> > @@ -7,6 +7,7 @@
> >   * Copyright (C) 2009 Intel Corporation, Yu Zhao <yu.zhao@xxxxxxxxx>
> >   */
> >  
> > +#include <linux/bitfield.h>
> >  #include <linux/pci.h>
> >  #include <linux/slab.h>
> >  #include <linux/export.h>
> > @@ -830,6 +831,7 @@ static int sriov_init(struct pci_dev *dev, int pos)
> >  	pci_read_config_byte(dev, pos + PCI_SRIOV_FUNC_LINK, &iov->link);
> >  	if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END)
> >  		iov->link = PCI_DEVFN(PCI_SLOT(dev->devfn), iov->link);
> > +	iov->vf_rebar_cap = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_VF_REBAR);
> >  
> >  	if (pdev)
> >  		iov->dev = pci_dev_get(pdev);
> > @@ -868,6 +870,30 @@ static void sriov_release(struct pci_dev *dev)
> >  	dev->sriov = NULL;
> >  }
> >  
> > +static void sriov_restore_vf_rebar_state(struct pci_dev *dev)
> > +{
> > +	unsigned int pos, nbars, i;
> > +	u32 ctrl;
> > +
> > +	pos = dev->sriov->vf_rebar_cap;
> > +	if (!pos)
> > +		return;
> > +
> > +	pci_read_config_dword(dev, pos + PCI_REBAR_CTRL, &ctrl);
> > +	nbars = FIELD_GET(PCI_REBAR_CTRL_NBAR_MASK, ctrl);
> > +
> > +	for (i = 0; i < nbars; i++, pos += 8) {
> > +		int bar_idx, size;
> > +
> > +		pci_read_config_dword(dev, pos + PCI_REBAR_CTRL, &ctrl);
> > +		bar_idx = FIELD_GET(PCI_REBAR_CTRL_BAR_IDX, ctrl);
> > +		size = pci_rebar_bytes_to_size(dev->sriov->barsz[bar_idx]);
> > +		ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE;
> > +		ctrl |= FIELD_PREP(PCI_REBAR_CTRL_BAR_SIZE, size);
> > +		pci_write_config_dword(dev, pos + PCI_REBAR_CTRL, ctrl);
> 
> I started to wonder if we'd still want to have the VF Rebar ones in 
> uapi/linux/pci_regs.h (despite the same capability layout):
> 
> /*
>  * PCI Resizable BAR and PCI VF Resizable BAR extended capabilities have 
>  * the same layout of fields.
>  */
> #define PCI_VF_REBAR_CTRL		PCI_REBAR_CTRL
> #define PCI_VF_REBAR_CTRL_BAR_IDX	PCI_REBAR_CTRL_BAR_IDX
> etc.
> 
> as then it would be possible grep to pick up only the relevant lines.
> 
> I'd not duplicate _SHIFT defines though. FIELD_PREP/GET() in general does 
> not need _SHIFT defines at all and they are just duplicated information.
> 
> > +	}
> > +}
> > +
> >  static void sriov_restore_state(struct pci_dev *dev)
> >  {
> >  	int i;
> > @@ -1027,8 +1053,10 @@ resource_size_t pci_sriov_resource_alignment(struct pci_dev *dev, int resno)
> >   */
> >  void pci_restore_iov_state(struct pci_dev *dev)
> >  {
> > -	if (dev->is_physfn)
> > +	if (dev->is_physfn) {
> > +		sriov_restore_vf_rebar_state(dev);
> >  		sriov_restore_state(dev);
> > +	}
> >  }
> >  
> >  /**
> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> > index b81e99cd4b62a..adc54bb2c8b34 100644
> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -482,6 +482,7 @@ struct pci_sriov {
> >  	u16		subsystem_vendor; /* VF subsystem vendor */
> >  	u16		subsystem_device; /* VF subsystem device */
> >  	resource_size_t	barsz[PCI_SRIOV_NUM_BARS];	/* VF BAR size */
> > +	u16		vf_rebar_cap;	/* VF Resizable BAR capability offset */
> >  	bool		drivers_autoprobe; /* Auto probing of VFs by driver */
> >  };
> >  
> > diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> > index ba326710f9c8b..bb2a334e50386 100644
> > --- a/include/uapi/linux/pci_regs.h
> > +++ b/include/uapi/linux/pci_regs.h
> > @@ -745,6 +745,7 @@
> >  #define PCI_EXT_CAP_ID_L1SS	0x1E	/* L1 PM Substates */
> >  #define PCI_EXT_CAP_ID_PTM	0x1F	/* Precision Time Measurement */
> >  #define PCI_EXT_CAP_ID_DVSEC	0x23	/* Designated Vendor-Specific */
> > +#define PCI_EXT_CAP_ID_VF_REBAR 0x24	/* VF Resizable BAR */
> >  #define PCI_EXT_CAP_ID_DLF	0x25	/* Data Link Feature */
> >  #define PCI_EXT_CAP_ID_PL_16GT	0x26	/* Physical Layer 16.0 GT/s */
> >  #define PCI_EXT_CAP_ID_NPEM	0x29	/* Native PCIe Enclosure Management */
> 
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> 
>