Re: [Intel-wired-lan] [PATCH iwl-net v3] ixgbevf: fix link speed reporting for Hyper-V E610 VFs

On 8/6/26 12:46, Tomasz Lichwala wrote:
> When an E610 VF is running under Hyper-V, the VFLINKS register does not
> carry valid link speed. The existing code reads speed from VFLINKS, which
> does not reflect the actual negotiated speed. This results in ethtool
> reporting a stale or incorrect link speed.
> 
> The Hyper-V synthetic NIC exposes the actual link status through
> emulated PCI config space at offset 0x209 in VFLINKS register format.
> Read and decode link status from there when checking link on E610 VFs.
> 
> Fixes: 4c44b450c69b ("ixgbevf: Add support for Intel(R) E610 device")
> Reviewed-by: Marcin Szycik <[email protected]>
> Signed-off-by: Tomasz Lichwala <[email protected]>
> ---

next time please provide changelog section here

>   drivers/net/ethernet/intel/ixgbevf/vf.c | 77 +++++++++++++++++++++----
>   1 file changed, 65 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ixgbevf/vf.c b/drivers/net/ethernet/intel/ixgbevf/vf.c
> index f6df86d124b9..8ad06e28b5de 100644
> --- a/drivers/net/ethernet/intel/ixgbevf/vf.c
> +++ b/drivers/net/ethernet/intel/ixgbevf/vf.c
> @@ -1,14 +1,17 @@
>   // SPDX-License-Identifier: GPL-2.0
>   /* Copyright(c) 1999 - 2024 Intel Corporation. */
>   
> +#include <linux/unaligned.h>
> +
>   #include "vf.h"
>   #include "ixgbevf.h"
>   

[..]

> +static s32 ixgbevf_hv_read_links_e610(struct ixgbe_hw *hw, u32 *links_reg)
> +{
> +	struct ixgbevf_adapter *adapter = hw->back;
> +	u8 data[IXGBE_HV_LINK_STATUS_SIZE];

following Paul's suggestion, you could add:
	if (IS_ENABLED(CONFIG_PCI_MMCONFIG)) {
		dev_err_once(&adapter->pdev->dev, "cannot read link status, 
PCI_MMCONFIG is required for Hyper-V\n");
		return -EOPNOTSUPP;
	}

and this will give user more information

IS_ENABLED() is really nice macro :)

> +
> +	for (int i = 0; i < IXGBE_HV_LINK_STATUS_SIZE; i++) {
> +		int ret = pci_read_config_byte(adapter->pdev,
> +					       IXGBE_HV_LINK_STATUS_OFFSET + i,
> +					       &data[i]);
> +		if (ret)
> +			return pcibios_err_to_errno(ret);
> +	}
> +
> +	*links_reg = get_unaligned_le32(data);
> +	return 0;
> +}
> +