2017-07-11 21:35:21

by Tushar Dave

Subject: [sparc-next] SPARC64: Fix sun4v DMA panic

64bit DMA only supported on sun4v equipped with ATU IOMMU HW.
'Commit b02c2b0bfd7ae ("sparc: remove arch specific dma_supported
implementations")' introduced a code that incorrectly allow
dma_supported() to succeed for 64bit dma mask even if system doesn't
have ATU IOMMU. This results into panic.

Fix it.

Reported-by: Meelis Roos <[email protected]>
Signed-off-by: Tushar Dave <[email protected]>
---
arch/sparc/kernel/pci_sun4v.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/sparc/kernel/pci_sun4v.c b/arch/sparc/kernel/pci_sun4v.c
index 24f21c7..f10e2f7 100644
--- a/arch/sparc/kernel/pci_sun4v.c
+++ b/arch/sparc/kernel/pci_sun4v.c
@@ -673,12 +673,14 @@ static void dma_4v_unmap_sg(struct device *dev, struct scatterlist *sglist,
static int dma_4v_supported(struct device *dev, u64 device_mask)
{
struct iommu *iommu = dev->archdata.iommu;
- u64 dma_addr_mask;
+ u64 dma_addr_mask = iommu->dma_addr_mask;

- if (device_mask > DMA_BIT_MASK(32) && iommu->atu)
- dma_addr_mask = iommu->atu->dma_addr_mask;
- else
- dma_addr_mask = iommu->dma_addr_mask;
+ if (device_mask > DMA_BIT_MASK(32)) {
+ if (iommu->atu)
+ dma_addr_mask = iommu->atu->dma_addr_mask;
+ else
+ return 0;
+ }

if ((device_mask & dma_addr_mask) == dma_addr_mask)
return 1;
--
1.9.1

2017-07-12 07:21:21

by Christoph Hellwig

Subject: Re: [sparc-next] SPARC64: Fix sun4v DMA panic

On Tue, Jul 11, 2017 at 02:34:47PM -0700, Tushar Dave wrote:
> 64bit DMA only supported on sun4v equipped with ATU IOMMU HW.
> 'Commit b02c2b0bfd7ae ("sparc: remove arch specific dma_supported
> implementations")' introduced a code that incorrectly allow
> dma_supported() to succeed for 64bit dma mask even if system doesn't
> have ATU IOMMU. This results into panic.
>
> Fix it.
>
> Reported-by: Meelis Roos <[email protected]>
> Signed-off-by: Tushar Dave <[email protected]>
> ---
> arch/sparc/kernel/pci_sun4v.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/arch/sparc/kernel/pci_sun4v.c b/arch/sparc/kernel/pci_sun4v.c
> index 24f21c7..f10e2f7 100644
> --- a/arch/sparc/kernel/pci_sun4v.c
> +++ b/arch/sparc/kernel/pci_sun4v.c
> @@ -673,12 +673,14 @@ static void dma_4v_unmap_sg(struct device *dev, struct scatterlist *sglist,
> static int dma_4v_supported(struct device *dev, u64 device_mask)
> {
> struct iommu *iommu = dev->archdata.iommu;
> - u64 dma_addr_mask;
> + u64 dma_addr_mask = iommu->dma_addr_mask;
>
> - if (device_mask > DMA_BIT_MASK(32) && iommu->atu)
> - dma_addr_mask = iommu->atu->dma_addr_mask;
> - else
> - dma_addr_mask = iommu->dma_addr_mask;
> + if (device_mask > DMA_BIT_MASK(32)) {
> + if (iommu->atu)
> + dma_addr_mask = iommu->atu->dma_addr_mask;
> + else
> + return 0;
> + }

This would be more readable as:

if (device_mask > DMA_BIT_MASK(32)) {
if (!iommu->atu)
return 0;
dma_addr_mask = iommu->atu->dma_addr_mask;
}

But except for that it looks fine to me:

Reviewed-by: Christoph Hellwig <[email protected]>

2017-07-12 15:13:23

by David Miller

Subject: Re: [sparc-next] SPARC64: Fix sun4v DMA panic

From: Tushar Dave <[email protected]>
Date: Tue, 11 Jul 2017 14:34:47 -0700

> 64bit DMA only supported on sun4v equipped with ATU IOMMU HW.
> 'Commit b02c2b0bfd7ae ("sparc: remove arch specific dma_supported
> implementations")' introduced a code that incorrectly allow
> dma_supported() to succeed for 64bit dma mask even if system doesn't
> have ATU IOMMU. This results into panic.
>
> Fix it.
>
> Reported-by: Meelis Roos <[email protected]>
> Signed-off-by: Tushar Dave <[email protected]>

Applied to the 'sparc' tree, thanks.