On Mon, Apr 24, 2017 at 09:23:16PM +0530, Sunil Kovvuri wrote: > On Mon, Apr 24, 2017 at 8:14 PM, Will Deacon <will.dea...@arm.com> wrote: > > On Mon, Apr 17, 2017 at 05:27:26PM +0530, sunil.kovv...@gmail.com wrote: > >> From: Sunil Goutham <sgout...@cavium.com> > >> > >> For software initiated address translation, when domain type is > >> IOMMU_DOMAIN_IDENTITY i.e SMMU is bypassed, mimic HW behavior > >> i.e return the same IOVA as translated address. > >> > >> This patch is an extension to Will Deacon's patchset > >> "Implement SMMU passthrough using the default domain". > > > > Are you actually seeing an issue here? If so, why isn't SMMUv3 affected too? > Yes and SMMUv3 should also be effected but as of now I don't see any use case. > If needed, i can re-submit the patch with changes in SMMUv3 as well.
Yes, please. > >> Signed-off-by: Sunil Goutham <sgout...@cavium.com> > >> --- > >> drivers/iommu/arm-smmu.c | 3 +++ > >> 1 file changed, 3 insertions(+) > >> > >> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c > >> index 41afb07..2f4a130 100644 > >> --- a/drivers/iommu/arm-smmu.c > >> +++ b/drivers/iommu/arm-smmu.c > >> @@ -1405,6 +1405,9 @@ static phys_addr_t arm_smmu_iova_to_phys(struct > >> iommu_domain *domain, > >> struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain); > >> struct io_pgtable_ops *ops= smmu_domain->pgtbl_ops; > >> > >> + if (domain->type == IOMMU_DOMAIN_IDENTITY) > >> + return iova; > >> + > >> if (!ops) > >> return 0; > > > > I'd have thought ops would be NULL, since arm_smmu_init_domain_context > > doesn't allocate them for an identity domain. > Yes ops is set to NULL. Argh, sorry, I completely overlooked that we return 0 in that case, rather than the iova. > > I don't understand this patch. Please can you explain the problem more > > clearly? > AFAIK for any driver outside IOMMU there is only one way to identify > if device is attached to > IOMMU or not and that is by checking iommu_domain. And I don't think > it would be appropriate > for the driver to check domain->type before calling 'iommu_iova_to_phys()' > API. > > The difference between IOMMU disabled and IOMMU being in passthrough > mode is that, in the > later case device is still attached to default domain but in former's > case it's NULL. So there is no > way to differentiate for the external driver whether IOMMU is in > passthrough mode or DMA mode. > > And since ops is NULL in passthrough mode, 'iommu_iova_to_phys()' will > return zero. > > Use case for your reference > https://lkml.org/lkml/2017/3/7/299 > This driver is for a NIC interface on platform which supports SMMUv2. Blimey, that driver is horrible, but I take your point on the API. Please repost, fixing SMMUv3 at the same time. Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
