| Message ID | 20210420045404.438735-1-leobras.c@gmail.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | [1/1] powerpc/pseries/iommu: Fix window size for direct mapping with pmem | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (40f5c8e99b3f2f53db08055f415af2aac416360e) |
| snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
| snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 8 lines checked |
| snowpatch_ozlabs/needsstable | warning | Please consider tagging this patch for stable! |
On 20/04/2021 14:54, Leonardo Bras wrote: > As of today, if the DDW is big enough to fit (1 << MAX_PHYSMEM_BITS) it's > possible to use direct DMA mapping even with pmem region. > > But, if that happens, the window size (len) is set to > (MAX_PHYSMEM_BITS - page_shift) instead of MAX_PHYSMEM_BITS, causing a > pagesize times smaller DDW to be created, being insufficient for correct > usage. > > Fix this so the correct window size is used in this case. Good find indeed. afaict this does not create a huge problem though as query.largest_available_block is always smaller than (MAX_PHYSMEM_BITS - page_shift) where it matters (phyp). Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru> > Fixes: bf6e2d562bbc4("powerpc/dma: Fallback to dma_ops when persistent memory present") > Signed-off-by: Leonardo Bras <leobras.c@gmail.com> > --- > arch/powerpc/platforms/pseries/iommu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c > index 9fc5217f0c8e..836cbbe0ecc5 100644 > --- a/arch/powerpc/platforms/pseries/iommu.c > +++ b/arch/powerpc/platforms/pseries/iommu.c > @@ -1229,7 +1229,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) > if (pmem_present) { > if (query.largest_available_block >= > (1ULL << (MAX_PHYSMEM_BITS - page_shift))) > - len = MAX_PHYSMEM_BITS - page_shift; > + len = MAX_PHYSMEM_BITS; > else > dev_info(&dev->dev, "Skipping ibm,pmemory"); > } >
On Tue, 2021-04-20 at 15:18 +1000, Alexey Kardashevskiy wrote: > > On 20/04/2021 14:54, Leonardo Bras wrote: > > As of today, if the DDW is big enough to fit (1 << MAX_PHYSMEM_BITS) it's > > possible to use direct DMA mapping even with pmem region. > > > > But, if that happens, the window size (len) is set to > > (MAX_PHYSMEM_BITS - page_shift) instead of MAX_PHYSMEM_BITS, causing a > > pagesize times smaller DDW to be created, being insufficient for correct > > usage. > > > > Fix this so the correct window size is used in this case. > > Good find indeed. > > afaict this does not create a huge problem though as > query.largest_available_block is always smaller than (MAX_PHYSMEM_BITS - > page_shift) where it matters (phyp). > > > Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru> > Thanks for reviewing! Leonardo Bras
On Tue, 20 Apr 2021 01:54:04 -0300, Leonardo Bras wrote: > As of today, if the DDW is big enough to fit (1 << MAX_PHYSMEM_BITS) it's > possible to use direct DMA mapping even with pmem region. > > But, if that happens, the window size (len) is set to > (MAX_PHYSMEM_BITS - page_shift) instead of MAX_PHYSMEM_BITS, causing a > pagesize times smaller DDW to be created, being insufficient for correct > usage. > > [...] Applied to powerpc/next. [1/1] powerpc/pseries/iommu: Fix window size for direct mapping with pmem https://git.kernel.org/powerpc/c/a9d2f9bb225fd2a764aef57738ab6c7f38d782ae cheers
diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c index 9fc5217f0c8e..836cbbe0ecc5 100644 --- a/arch/powerpc/platforms/pseries/iommu.c +++ b/arch/powerpc/platforms/pseries/iommu.c @@ -1229,7 +1229,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) if (pmem_present) { if (query.largest_available_block >= (1ULL << (MAX_PHYSMEM_BITS - page_shift))) - len = MAX_PHYSMEM_BITS - page_shift; + len = MAX_PHYSMEM_BITS; else dev_info(&dev->dev, "Skipping ibm,pmemory"); }
As of today, if the DDW is big enough to fit (1 << MAX_PHYSMEM_BITS) it's possible to use direct DMA mapping even with pmem region. But, if that happens, the window size (len) is set to (MAX_PHYSMEM_BITS - page_shift) instead of MAX_PHYSMEM_BITS, causing a pagesize times smaller DDW to be created, being insufficient for correct usage. Fix this so the correct window size is used in this case. Fixes: bf6e2d562bbc4("powerpc/dma: Fallback to dma_ops when persistent memory present") Signed-off-by: Leonardo Bras <leobras.c@gmail.com> --- arch/powerpc/platforms/pseries/iommu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)