netdev - Re: [PATCH net-next v2 2/3] PCI/VPD: Change Chelsio T4 quirk to provide access to full virtual address space

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Message-ID: <CAKgT0UcBoXv5mGr9NFxusqX16mqi3Nr7+2BUZL0=z6Js8d9A7Q@mail.gmail.com>
Date:   Mon, 8 Feb 2021 08:59:13 -0800
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Raju Rangoju <rajur@...lsio.com>, Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2 2/3] PCI/VPD: Change Chelsio T4 quirk to
 provide access to full virtual address space

On Fri, Feb 5, 2021 at 2:15 PM Heiner Kallweit <hkallweit1@...il.com> wrote:
>
> cxgb4 uses the full VPD address space for accessing its EEPROM (with some
> mapping, see t4_eeprom_ptov()). In cudbg_collect_vpd_data() it sets the
> VPD len to 32K (PCI_VPD_MAX_SIZE), and then back to 2K (CUDBG_VPD_PF_SIZE).
> Having official (structured) and inofficial (unstructured) VPD data
> violates the PCI spec, let's set VPD len according to all data that can be
> accessed via PCI VPD access, no matter of its structure.
>
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> ---
>  drivers/pci/vpd.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pci/vpd.c b/drivers/pci/vpd.c
> index 7915d10f9..06a7954d0 100644
> --- a/drivers/pci/vpd.c
> +++ b/drivers/pci/vpd.c
> @@ -633,9 +633,8 @@ static void quirk_chelsio_extend_vpd(struct pci_dev *dev)
>         /*
>          * If this is a T3-based adapter, there's a 1KB VPD area at offset
>          * 0xc00 which contains the preferred VPD values.  If this is a T4 or
> -        * later based adapter, the special VPD is at offset 0x400 for the
> -        * Physical Functions (the SR-IOV Virtual Functions have no VPD
> -        * Capabilities).  The PCI VPD Access core routines will normally
> +        * later based adapter, provide access to the full virtual EEPROM
> +        * address space. The PCI VPD Access core routines will normally
>          * compute the size of the VPD by parsing the VPD Data Structure at
>          * offset 0x000.  This will result in silent failures when attempting
>          * to accesses these other VPD areas which are beyond those computed
> @@ -644,7 +643,7 @@ static void quirk_chelsio_extend_vpd(struct pci_dev *dev)
>         if (chip == 0x0 && prod >= 0x20)
>                 pci_set_vpd_size(dev, 8192);
>         else if (chip >= 0x4 && func < 0x8)
> -               pci_set_vpd_size(dev, 2048);
> +               pci_set_vpd_size(dev, PCI_VPD_MAX_SIZE);
>  }
>
>  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_CHELSIO, PCI_ANY_ID,

So as I recall the size value was added when some hardware was hanging
when an out-of-bounds read occured from various tools accessing the
VPD. I'm assuming if you are enabling full access the T4 hardware can
handle cases where an out-of-bounds read is requested?

Otherwise the code itself looks fine to me.

Reviewed-by: Alexander Duyck <alexanderduyck@...com>