Hi Robin,
On 4/13/2017 7:21 AM, Robin Murphy wrote:
Hi Nate,
On 13/04/17 09:55, Nate Watterson wrote:
Currently, the __iommu_dma_{map/free} functions call iova_{offset/align}
making them unsuitable for use with iommu_domains having an IOMMU_DMA_MSI
cookie since the cookie's iova_domain member, iovad, is uninitialized.
Now that iommu_dma_get_msi_page() calls __iommu_dma_map() regardless
of cookie type, failures are being seen when mapping MSI target
addresses for devices attached to UNMANAGED domains. To work around
this issue, the iova_domain granule for IOMMU_DMA_MSI cookies is
initialized to the value returned by cookie_msi_granule().
Oh bum. Thanks for the report.
However, I really don't like bodging around it with deliberate undefined
behaviour. Fixing things properly doesn't seem too hard:
I was not especially please with my solution, but I wanted to avoid
potentially missing any other spots in the code where granule was
used uninitialized. The compile time check made me feel a little
less dirty about innappropriately using the iova_domain with MSI
cookies.
----->8-----
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 8348f366ddd1..62618e77bedc 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -396,13 +396,13 @@ static void iommu_dma_free_iova(struct
iommu_dma_cookie *cookie,
dma_addr_t iova, size_t size)
{
struct iova_domain *iovad = &cookie->iovad;
- unsigned long shift = iova_shift(iovad);
/* The MSI case is only ever cleaning up its most recent
allocation */
if (cookie->type == IOMMU_DMA_MSI_COOKIE)
cookie->msi_iova -= size;
else
- free_iova_fast(iovad, iova >> shift, size >> shift);
+ free_iova_fast(iovad, iova_pfn(iovad, iova),
+ size >> iova_shift(iovad));
}
static void __iommu_dma_unmap(struct iommu_domain *domain, dma_addr_t
dma_addr,
@@ -617,11 +617,14 @@ static dma_addr_t __iommu_dma_map(struct device
*dev, phys_addr_t phys,
{
struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
struct iommu_dma_cookie *cookie = domain->iova_cookie;
- struct iova_domain *iovad = &cookie->iovad;
- size_t iova_off = iova_offset(iovad, phys);
+ size_t iova_off = 0;
dma_addr_t iova;
- size = iova_align(iovad, size + iova_off);
+ if (cookie->type == IOMMU_DMA_IOVA_COOKIE) {
+ iova_off = iova_offset(&cookie->iovad, phys);
+ size = iova_align(&cookie->iovad, size + iova_off);
+ }
+
iova = iommu_dma_alloc_iova(domain, size, dma_get_mask(dev), dev);
if (!iova)
return DMA_ERROR_CODE;
-----8<-----
Untested, and you'll probably want to double-check it anyway given that
the original oversight was mine in the first place ;)
This looks good to me. As Shanker has already mentioned, it does fix the
faults we were previously seeing with direct device assignment. I also
verified that there aren't any other obvious cases of a granule == 0
being used in the dma_iommu code by adding BUG_ON(!iovad->granule) to
iova_{mask/align/offset/...} and running a variety of tests without
issue.
Are you going to post the patch?
Robin.
Fixes: a44e6657585b ("iommu/dma: Clean up MSI IOVA allocation")
Signed-off-by: Nate Watterson <nwatt...@codeaurora.org>
---
drivers/iommu/dma-iommu.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 8348f366..d7b0816 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -127,6 +127,16 @@ int iommu_get_msi_cookie(struct iommu_domain *domain,
dma_addr_t base)
cookie->msi_iova = base;
domain->iova_cookie = cookie;
+
+ /*
+ * Setup granule for compatibility with __iommu_dma_{alloc/free} and
+ * add a compile time check to ensure that writing granule won't
+ * clobber msi_iova.
+ */
+ cookie->iovad.granule = cookie_msi_granule(cookie);
+ BUILD_BUG_ON(offsetof(struct iova_domain, granule) <
+ sizeof(cookie->msi_iova));
+
return 0;
}
EXPORT_SYMBOL(iommu_get_msi_cookie);
--
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