linux-kernel - Re: [PATCH v5 1/6] PCI/IOV: Restore VF resizable BAR state after reset

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Message-ID: <d6e026ad-4dd4-2e03-6f8b-a10980fa0ce7@linux.intel.com>
Date: Thu, 13 Mar 2025 11:45:45 +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 v5 1/6] PCI/IOV: Restore VF resizable BAR state after
 reset

On Wed, 12 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.
> 
> 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             | 29 ++++++++++++++++++++++++++++-
>  include/uapi/linux/pci_regs.h |  1 +
>  2 files changed, 29 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 121540f57d4bf..eb4d33eacacb8 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>
> @@ -868,6 +869,30 @@ 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 = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_VF_REBAR);
> +	if (!pos)
> +		return;

FYI, the commit f7c9bb759161 ("PCI: Cache offset of Resizable BAR 
capability") which is currently in pci/enumeration makes this simpler.

> +	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);
> +	}
> +}
> +
>  static void sriov_restore_state(struct pci_dev *dev)
>  {
>  	int i;
> @@ -1027,8 +1052,10 @@ 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/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index 3c2558b98d225..aadd483c47d6f 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -744,6 +744,7 @@
>  #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 */
> 

-- 
 i.