linux-kernel - Re: [PATCH v2 17/24] PCI: vmd: Use RESPONSE_IS_PCI

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Date:   Fri, 15 Oct 2021 20:22:10 +0530
From:   Naveen Naidu <naveennaidu479@...il.com>
To:     bhelgaas@...gle.com
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jonathan Derrick <jonathan.derrick@...ux.dev>,
        Nirmal Patel <nirmal.patel@...ux.intel.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>
Subject: Re: [PATCH v2 17/24] PCI: vmd: Use RESPONSE_IS_PCI_ERROR() to check
 read from hardware

On 15/10, Naveen Naidu wrote:
> An MMIO read from a PCI device that doesn't exist or doesn't respond
> causes a PCI error.  There's no real data to return to satisfy the
> CPU read, so most hardware fabricates ~0 data.
> 
> Use RESPONSE_IS_PCI_ERROR() to check the response we get when we read
> data from hardware.
> 
> This helps unify PCI error response checking and make error checks
> consistent and easier to find.
> 
> Reviewed-by: Jonathan Derrick <jonathan.derrick@...ux.dev>
> Signed-off-by: Naveen Naidu <naveennaidu479@...il.com>
> ---
>  drivers/pci/controller/vmd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index a5987e52700e..db81bc4cfe8c 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -538,7 +538,7 @@ static int vmd_get_phys_offsets(struct vmd_dev *vmd, bool native_hint,
>  		int ret;
>  
>  		ret = pci_read_config_dword(dev, PCI_REG_VMLOCK, &vmlock);
> -		if (ret || vmlock == ~0)
> +		if (ret || RESPONSE_IS_PCI_ERROR(&vmlock))
>  			return -ENODEV;
>  
>  		if (MB2_SHADOW_EN(vmlock)) {
> -- 
> 2.25.1
> 

Jonathan, I have added your Reviewed-by tag from the first version [1] of
the patch series, since this patch did not change in the version 2. I
hope that's okay. If not, I really apologize for that and can you 
please let me know how to rectify that mistake.

[1]:
https://lore.kernel.org/linux-pci/f3aca934-7dee-b294-ad3c-264e773eddda@linux.dev/T/#u

Thanks,
Naveen