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Message-ID: <b10b559c-cb23-d21e-d6ee-e060eb0b6b5b@linux.intel.com>
Date: Wed, 26 Mar 2025 16:42:28 +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 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.
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>
--
i.
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