[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ZNZsWcV5asNwyOq8@ziepe.ca>
Date: Fri, 11 Aug 2023 14:14:01 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Baolu Lu <baolu.lu@...ux.intel.com>
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
Robin Murphy <robin.murphy@....com>,
Kevin Tian <kevin.tian@...el.com>,
Jean-Philippe Brucker <jean-philippe@...aro.org>,
Nicolin Chen <nicolinc@...dia.com>,
Yi Liu <yi.l.liu@...el.com>,
Jacob Pan <jacob.jun.pan@...ux.intel.com>,
iommu@...ts.linux.dev, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 12/12] iommu: Add helper to set iopf handler for domain
On Fri, Aug 11, 2023 at 10:40:15AM +0800, Baolu Lu wrote:
> On 2023/8/11 3:18, Jason Gunthorpe wrote:
> > On Thu, Jul 27, 2023 at 01:48:37PM +0800, Lu Baolu wrote:
> > > To avoid open code everywhere.
> > >
> > > Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> > > ---
> > > include/linux/iommu.h | 11 ++++++++++-
> > > drivers/iommu/iommu.c | 20 ++++++++++++++++++--
> > > 2 files changed, 28 insertions(+), 3 deletions(-)
> >
> > Seems like overkill at this point..
> >
> > Also, I think this is probably upside down.
> >
> > We want to create the domains as fault enabled in the first place.
> >
> > A fault enabled domain should never be attached to something that
> > cannot support faults. It should also not support changing the fault
> > handler while it exists.
> >
> > Thus at the creation point would be the time to supply the fault handler
> > as part of requesting faulting.
> >
> > Taking an existing domain and making it faulting enabled is going to
> > be really messy in all the corner cases.
>
> Yes. Agreed.
>
> >
> > My advice (and Robin will probably hate me), is to define a new op:
> >
> > struct domain_alloc_paging_args {
> > struct fault_handler *fault_handler;
> > void *fault_data
> > };
> >
> > struct iommu_domain *domain_alloc_paging2(struct device *dev, struct
> > domain_alloc_paging_args *args)
> >
> > The point would be to leave the majority of drivers using the
> > simplified, core assisted, domain_alloc_paging() interface and they
> > just don't have to touch any of this stuff at all.
> >
> > Obviously if handler is given then the domain will be initialized as
> > faulting.
>
> Perhaps we also need an internal helper for iommu drivers to check the
> iopf capability of the domain.
Yeah, maybe.
I've been mulling over this for a a bit here
Robin suggested to wrap everything in a arg to domain_alloc and build
a giant super multiplexor
I don't really like that because it makes it quite complicated for the
driver and multiplexor APIs are rarely good.
So for simple drivers I like the 'domain_alloc_paging' as the only op
they implement and it is obviously simple and hard to implement
wrong. Most drivers would do this.
We also need a:
struct iommu_domain *domain_alloc_sva(struct device *dev, struct mm_struct *mm)
So SVA can be fully setup at allocation time. SVA doesn't have any
legal permutations so it can be kept simple.
Then we need something to bundle:
- Dirty tracking yes/no
- The iommufd user space blob
- Fault handling yes/no
For complex drivers.
So maybe we should just have a 3rd option
// I'm a complex driver and many people checked that I implemented
// this right:
struct domain_alloc_args {
struct device *dev;
unsigned int flags; // For requesting dirty tracking
// alloc_domain_user interface
struct iommu_domain *parent;
void *user_data;
size_t user_len;
// Faulting
struct fault_handler *fault_handler;
void *fault_data;
};
struct iommu_domain *domain_alloc(struct domain_alloc_args *args);
?
IDK, multiplexor APIs are rarely good, but maybe this is the right
direction?
Jason
Powered by blists - more mailing lists