linux-kernel - Re: [PATCH v3 1/1] PCI: endpoint: pci-epf-vntb: Fix transfer failure for fixed size BARs

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Message-ID: <20240108082303.GA12822@thinkpad>
Date: Mon, 8 Jan 2024 13:53:03 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Frank Li <Frank.Li@....com>
Cc: mani@...nel.org, allenbh@...il.com, bhelgaas@...gle.com,
	dave.jiang@...el.com, imx@...ts.linux.dev, jdmason@...zu.us,
	kishon@...nel.org, kw@...ux.com, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, lpieralisi@...nel.org,
	ntb@...ts.linux.dev
Subject: Re: [PATCH v3 1/1] PCI: endpoint: pci-epf-vntb: Fix transfer failure
 for fixed size BARs

On Wed, Dec 20, 2023 at 02:24:27PM -0500, Frank Li wrote:
> For the inbound MEM/IO TLPs, iATU on the endpoint expects the target
> address to be aligned to the size of the BAR. For configurable BARs, there
> is no issue because both host and endpoint will know the exact size of the
> BAR region. But for fixed size BARs available in some controllers, if the
> BAR size advertised by the endpoint is not same as of the actual BAR size
> used in the controller, then the MEM/IO TLPs generated by the host will not
> be translated properly by the endpoint iATU.
> 
> So if the fixed size BARs are available in endpoint controllers, always use
> the actual BAR size.
> 

You should add a note saying that you are fixing the issue only for DB BAR and a
similar fix is needed for other MW BARs.

> Fixes: e35f56bb0330 ("PCI: endpoint: Support NTB transfer between RC and EP")
> Cc: stable@...r.kernel.org
> Signed-off-by: Frank Li <Frank.Li@....com>

With that,

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

- Mani

> ---
> 
> Notes:
>     Change from v2 to v3
>     - rework commti message
>     - add fixes and cc stable
>     - return -ENOMEN when request size > fix bar size
>     Change from v1 to v2
>     - Remove unnessary set align when fix_bar_size.
> 
>  drivers/pci/endpoint/functions/pci-epf-vntb.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> index 3f60128560ed0..85120978fb8c9 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> @@ -550,6 +550,14 @@ static int epf_ntb_db_bar_init(struct epf_ntb *ntb)
>  
>  	barno = ntb->epf_ntb_bar[BAR_DB];
>  
> +	if (epc_features->bar_fixed_size[barno]) {
> +		if (size > epc_features->bar_fixed_size[barno]) {
> +			dev_err(dev, "Fixed BAR%d is too small for doorbell\n", barno);
> +			return -ENOMEM;
> +		}
> +		size = epc_features->bar_fixed_size[barno];
> +	}
> +
>  	mw_addr = pci_epf_alloc_space(ntb->epf, size, barno, align, 0);
>  	if (!mw_addr) {
>  		dev_err(dev, "Failed to allocate OB address\n");
> -- 
> 2.34.1
> 
> 

-- 
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