Messages in this thread | | | Date | Wed, 20 Oct 2021 13:21:44 +0800 | Subject | Re: [PATCH v3 4/6] iommu: Move IOMMU pagesize check to attach_device | From | Lu Baolu <> |
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On 2021/10/20 0:37, Sven Peter via iommu wrote: > The iova allocator is capable of handling any granularity which is a power > of two. Remove the much stronger condition that the granularity must be > smaller or equal to the CPU page size from a BUG_ON there. > Instead, check this condition during __iommu_attach_device and fail > gracefully. > > Signed-off-by: Sven Peter<sven@svenpeter.dev> > --- > drivers/iommu/iommu.c | 35 ++++++++++++++++++++++++++++++++--- > drivers/iommu/iova.c | 7 ++++--- > include/linux/iommu.h | 5 +++++ > 3 files changed, 41 insertions(+), 6 deletions(-) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index dd7863e453a5..28896739964b 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -80,6 +80,8 @@ static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus, > unsigned type); > static int __iommu_attach_device(struct iommu_domain *domain, > struct device *dev); > +static void __iommu_detach_device(struct iommu_domain *domain, > + struct device *dev); > static int __iommu_attach_group(struct iommu_domain *domain, > struct iommu_group *group); > static void __iommu_detach_group(struct iommu_domain *domain, > @@ -1974,6 +1976,19 @@ void iommu_domain_free(struct iommu_domain *domain) > } > EXPORT_SYMBOL_GPL(iommu_domain_free); > > +static int iommu_check_page_size(struct iommu_domain *domain) > +{ > + if (!iommu_is_paging_domain(domain)) > + return 0; > + > + if (!(domain->pgsize_bitmap & (PAGE_SIZE | (PAGE_SIZE - 1)))) { > + pr_warn("IOMMU pages cannot exactly represent CPU pages.\n"); > + return -EFAULT; > + } > + > + return 0; > +} > + > static int __iommu_attach_device(struct iommu_domain *domain, > struct device *dev) > { > @@ -1983,9 +1998,23 @@ static int __iommu_attach_device(struct iommu_domain *domain, > return -ENODEV; > > ret = domain->ops->attach_dev(domain, dev); > - if (!ret) > - trace_attach_device_to_domain(dev); > - return ret; > + if (ret) > + return ret; > + > + /* > + * Check that CPU pages can be represented by the IOVA granularity. > + * This has to be done after ops->attach_dev since many IOMMU drivers > + * only limit domain->pgsize_bitmap after having attached the first > + * device. > + */ > + ret = iommu_check_page_size(domain); > + if (ret) { > + __iommu_detach_device(domain, dev); > + return ret; > + }
It looks odd. __iommu_attach_device() attaches an I/O page table for a device. How does it relate to CPU pages? Why is it a failure case if CPU page size is not covered?
Best regards, baolu
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