linux-kernel - Re: [PATCH] powerpc/pseries: Add a null judgment after iommu_pseries_alloc

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Message-ID: <87zgcgboel.fsf@mpe.ellerman.id.au>
Date:   Thu, 24 Nov 2022 22:08:34 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Deming Wang <wangdeming@...pur.com>
Cc:     benh@...nel.crashing.org, paulus@...ba.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Deming Wang <wangdeming@...pur.com>
Subject: Re: [PATCH] powerpc/pseries: Add a null judgment after
 iommu_pseries_alloc_group

Deming Wang <wangdeming@...pur.com> writes:
> We should avoid use the return value directly after  call
> iommu_pseries_alloc_group. Because it_may return a null.

We should probably at least print a warning in that case though?

Otherwise someone's PCI device will not work with no indication why, or
more likely the kernel will crash elsewhere with no indication that the
group allocation is the original cause.

cheers

> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> index fba64304e859..801eb9d4bdca 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -649,6 +649,9 @@ static void pci_dma_bus_setup_pSeries(struct pci_bus *bus)
>  	pci->phb->dma_window_base_cur = 0x8000000ul;
>  
>  	pci->table_group = iommu_pseries_alloc_group(pci->phb->node);
> +	if (!pci->table_group)
> +		return;
> +
>  	tbl = pci->table_group->tables[0];
>  
>  	iommu_table_setparms(pci->phb, dn, tbl);
> @@ -734,6 +737,9 @@ static void pci_dma_bus_setup_pSeriesLP(struct pci_bus *bus)
>  
>  	if (!ppci->table_group) {
>  		ppci->table_group = iommu_pseries_alloc_group(ppci->phb->node);
> +		if (!ppci->table_group)
> +			return;
> +
>  		tbl = ppci->table_group->tables[0];
>  		iommu_table_setparms_lpar(ppci->phb, pdn, tbl,
>  				ppci->table_group, dma_window);
> @@ -765,6 +771,9 @@ static void pci_dma_dev_setup_pSeries(struct pci_dev *dev)
>  
>  		pr_debug(" --> first child, no bridge. Allocating iommu table.\n");
>  		PCI_DN(dn)->table_group = iommu_pseries_alloc_group(phb->node);
> +		if (!PCI_DN(dn)->table_group)
> +			return;
> +
>  		tbl = PCI_DN(dn)->table_group->tables[0];
>  		iommu_table_setparms(phb, dn, tbl);
>  
> @@ -1521,6 +1530,9 @@ static void pci_dma_dev_setup_pSeriesLP(struct pci_dev *dev)
>  	pci = PCI_DN(pdn);
>  	if (!pci->table_group) {
>  		pci->table_group = iommu_pseries_alloc_group(pci->phb->node);
> +		if (!pci->table_group)
> +			return;
> +
>  		tbl = pci->table_group->tables[0];
>  		iommu_table_setparms_lpar(pci->phb, pdn, tbl,
>  				pci->table_group, dma_window);
> -- 
> 2.27.0