Re: [PATCH v5 09/12] iommu: Make iommu_queue_iopf() more generic

[Baolu Lu]

On 9/22/23 7:34 AM, Jason Gunthorpe wrote:
> On Thu, Sep 21, 2023 at 11:25:56PM +0800, Liu, Jingqi wrote:
> > On 9/14/2023 4:56 PM, Lu Baolu wrote:
> > > Make iommu_queue_iopf() more generic by making the iopf_group a minimal
> > > set of iopf's that an iopf handler of domain should handle and respond
> > > to. Add domain parameter to struct iopf_group so that the handler can
> > > retrieve and use it directly.
> > >
> > > Change iommu_queue_iopf() to forward groups of iopf's to the domain's
> > > iopf handler. This is also a necessary step to decouple the sva iopf
> > > handling code from this interface.
> > >
> > > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > > ---
> > >    include/linux/iommu.h      |  4 ++--
> > >    drivers/iommu/iommu-sva.h  |  6 ++---
> > >    drivers/iommu/io-pgfault.c | 49 ++++++++++++++++++++++++++++----------
> > >    drivers/iommu/iommu-sva.c  |  3 +--
> > >    4 files changed, 42 insertions(+), 20 deletions(-)
> > ......
> >
> > > @@ -112,6 +110,7 @@ int iommu_queue_iopf(struct iommu_fault *fault, struct device *dev)
> > >    {
> > >    	int ret;
> > >    	struct iopf_group *group;
> > > +	struct iommu_domain *domain;
> > >    	struct iopf_fault *iopf, *next;
> > >    	struct iommu_fault_param *iopf_param;
> > >    	struct dev_iommu *param = dev->iommu;
> > > @@ -143,6 +142,19 @@ int iommu_queue_iopf(struct iommu_fault *fault, struct device *dev)
> > >    		return 0;
> > >    	}
> > > +	if (fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID)
> > > +		domain = iommu_get_domain_for_dev_pasid(dev, fault->prm.pasid, 0);
> > > +	else
> > > +		domain = iommu_get_domain_for_dev(dev);
> > > +
> > > +	if (!domain || !domain->iopf_handler) {
> >
> > Does it need to check if 'domain' is error ?  Like below:
> >
> >           if (!domain || IS_ERR(domain) || !domain->iopf_handler)
>
> Urk, yes, but not like that
>
> The IF needs to be moved into the else block as each individual
> function has its own return convention.

iommu_get_domain_for_dev_pasid() returns an ERR_PTR only if the matching
domain type is specified (non-zero).

Adding IS_ERR(domain) in the else block will make the code more
readable. Alternatively we can put a comment around above code to
explain that ERR_PTR is not a case here.

Best regards,
baolu