linux-kernel - Re: [PATCH v2] iommu/dma: Fix IOVA reserve dma ranges

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Message-ID: <20200911151659.GA868760@bjorn-Precision-5520>
Date:   Fri, 11 Sep 2020 10:16:59 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Srinath Mannam <srinath.mannam@...adcom.com>
Cc:     Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, poza@...eaurora.org,
        bcm-kernel-feedback-list@...adcom.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iommu/dma: Fix IOVA reserve dma ranges

On Fri, Sep 11, 2020 at 03:55:34PM +0530, Srinath Mannam wrote:
> Fix IOVA reserve failure in the case when address of first memory region
> listed in dma-ranges is equal to 0x0.
> 
> Fixes: aadad097cd46f ("iommu/dma: Reserve IOVA for PCIe inaccessible DMA address")
> Signed-off-by: Srinath Mannam <srinath.mannam@...adcom.com>
> ---
> Changes from v1:
>    Removed unnecessary changes based on Robin's review comments.
> 
>  drivers/iommu/dma-iommu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 5141d49a046b..682068a9aae7 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -217,7 +217,7 @@ static int iova_reserve_pci_windows(struct pci_dev *dev,
>  			lo = iova_pfn(iovad, start);
>  			hi = iova_pfn(iovad, end);
>  			reserve_iova(iovad, lo, hi);
> -		} else {
> +		} else if (end < start) {
>  			/* dma_ranges list should be sorted */
>  			dev_err(&dev->dev, "Failed to reserve IOVA\n");

You didn't actually change the error message, but the message would be
way more useful if it included the IOVA address range, e.g., the
format used in pci_register_host_bridge():

  bus address [%#010llx-%#010llx]

Incidentally, the pr_err() in copy_reserved_iova() looks bogus; it
prints iova->pfn_low twice, when it should probably print the base and
size or (my preference) something like the above:

        pr_err("Reserve iova range %lx@%lx failed\n",
               iova->pfn_lo, iova->pfn_lo);

>  			return -EINVAL;
> -- 
> 2.17.1
>