Re: [PATCH v7 05/10] PCI: endpoint: pci-epf-vntb: Export endpoint DMA channels

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] PCI: endpoint: pci-epf-vntb: return error in epf_ntb_dma_set_bar() when !dma
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commit 31737c4f08c2b9d1daab53d00daf98b9d845d441
Author: Koichiro Den <den@valinux.co.jp>

PCI: endpoint: pci-epf-vntb: Export endpoint DMA channels

This commit adds support for exporting endpoint-local DMA read channels to
the RC through a configurable dma_bar configfs attribute and a control-region
extension. When configured, it reserves the read direction channels, maps
unassigned resources through the selected BAR, and adds the
EPF_NTB_COMMAND_SETUP_DMA_BAR command to install the BAR submappings.

> diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> index 3adbaa9d85db2..ac83af54122f7 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c

[ ... ]

> +static int epf_ntb_dma_set_bar(struct epf_ntb *ntb)
> +{
> +	struct pci_epf_bar_submap *old_submap;
> +	struct epf_ntb_dma *dma = ntb->dma;
> +	unsigned int old_num_submap;
> +	struct pci_epf_bar *bar;
> +	int restore, ret;
> +
> +	if (!dma)
> +		return 0;

[Severity: Medium]
Should epf_ntb_dma_set_bar() return a negative error code (such as -EINVAL
or -EOPNOTSUPP) instead of 0 when dma is NULL?

When dma_bar is left unassigned (NO_BAR), epf_ntb_dma_collect() leaves
ntb->dma as NULL. The only caller of epf_ntb_dma_set_bar() is
epf_ntb_cmd_handler() when servicing EPF_NTB_COMMAND_SETUP_DMA_BAR:

	case EPF_NTB_COMMAND_SETUP_DMA_BAR:
		ret = epf_ntb_dma_set_bar(ntb);
		ctrl->command_status = ret ? EPF_NTB_COMMAND_STATUS_ERROR :
					     EPF_NTB_COMMAND_STATUS_OK;
		break;

Returning 0 here causes epf_ntb_cmd_handler() to report
EPF_NTB_COMMAND_STATUS_OK to the host peer even though DMA export is
disabled and no DMA BAR was configured.

[ ... ]

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Sashiko AI review · https://sashiko.dev/#/patchset/20261021042229.2280937-1-den@valinux.co.jp?part=5