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Message-ID: <d4mnsiiq3hjnpan3ue5e36ibu2kjuspsbq74viilwtoetljyyl@dabmlm6yu6e5>
Date: Wed, 2 Apr 2025 12:20:13 +0200
From: Michał Winiarski <michal.winiarski@...el.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.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, Mar 26, 2025 at 04:52:22PM +0200, Ilpo Järvinen wrote:
> 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.
Yeah - I'll change it to refer to r6.2:
"See PCIe r6.2, sec 7.8.7."
>
> --
> 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.
And I'll also add the defines for VF_REBAR and usage for config space
restore.
Thanks,
-Michał
> >
> > > + }
> > > +}
> > > +
> > > 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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