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Message-ID: <f12b85eb-0dad-fa48-ffca-d052f41e0a28@linux.intel.com>
Date: Wed, 26 Mar 2025 16:52:22 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Michał Winiarski <michal.winiarski@...el.com>
cc: linux-pci@...r.kernel.org, intel-xe@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org, LKML <linux-kernel@...r.kernel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Christian König <christian.koenig@....com>,
Krzysztof Wilczyński <kw@...ux.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Michal Wajdeczko <michal.wajdeczko@...el.com>,
Lucas De Marchi <lucas.demarchi@...el.com>,
Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>, Matt Roper <matthew.d.roper@...el.com>
Subject: Re: [PATCH v6 1/6] PCI/IOV: Restore VF resizable BAR state after
reset
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@...el.com>
> > Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> > Reviewed-by: Christian König <christian.koenig@....com>
> > ---
> > 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@...el.com>
> > */
> >
> > +#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@...ux.intel.com>
>
>
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