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

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Date:   Mon, 14 Sep 2020 12:41:10 +0530
From:   Srinath Mannam <srinath.mannam@...adcom.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
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 <bcm-kernel-feedback-list@...adcom.com>,
        iommu@...ts.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] iommu/dma: Fix IOVA reserve dma ranges

On Fri, Sep 11, 2020 at 8:47 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
Hi Bjorn,
Thanks for review.
> 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");
>
It is very unlikely to come to this error, dma_ranges list is sorted
in "devm_of_pci_get_host_bridge_resources" function.
> 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]
I will add this change and send the next patchset.

Thanks & Regards,
Srinath.
>
> 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
> >