linux-kernel - Re: [PATCH v4 1/7] PCI/IOV: Restore VF resizable BAR state after reset

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Message-ID: <7413545c-62e3-4d27-8522-ea6f579c8195@amd.com>
Date: Tue, 29 Oct 2024 14:01:52 +0100
From: Christian König <christian.koenig@....com>
To: Michał Winiarski <michal.winiarski@...el.com>,
 linux-pci@...r.kernel.org, intel-xe@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 Bjorn Helgaas <bhelgaas@...gle.com>, Krzysztof Wilczyński
 <kw@...ux.com>, Ilpo Järvinen
 <ilpo.jarvinen@...ux.intel.com>
Cc: 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 v4 1/7] PCI/IOV: Restore VF resizable BAR state after
 reset

Am 25.10.24 um 23:50 schrieb Michał Winiarski:
> 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 aaa33e8dc4c97..6bdc9950b9787 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>
> @@ -862,6 +863,30 @@ 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;
> +
> +	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;
> @@ -1021,8 +1046,10 @@ 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 12323b3334a9c..a0cf701c4c3af 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -740,6 +740,7 @@
>   #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 */