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Message-ID: <20210524161129.085503ad@x1.home.shazbot.org>
Date: Mon, 24 May 2021 16:11:29 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Shenming Lu <lushenming@...wei.com>
Cc: Eric Auger <eric.auger@...hat.com>,
Cornelia Huck <cohuck@...hat.com>,
Will Deacon <will@...nel.org>,
"Robin Murphy" <robin.murphy@....com>,
Joerg Roedel <joro@...tes.org>,
"Jean-Philippe Brucker" <jean-philippe@...aro.org>,
<kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<iommu@...ts.linux-foundation.org>, <linux-api@...r.kernel.org>,
Kevin Tian <kevin.tian@...el.com>,
Lu Baolu <baolu.lu@...ux.intel.com>, <yi.l.liu@...el.com>,
Christoph Hellwig <hch@...radead.org>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Barry Song <song.bao.hua@...ilicon.com>,
<wanghaibin.wang@...wei.com>, <yuzenghui@...wei.com>
Subject: Re: [RFC PATCH v3 8/8] vfio: Add nested IOPF support
On Mon, 24 May 2021 21:11:11 +0800
Shenming Lu <lushenming@...wei.com> wrote:
> On 2021/5/21 15:59, Shenming Lu wrote:
> > On 2021/5/19 2:58, Alex Williamson wrote:
> >> On Fri, 9 Apr 2021 11:44:20 +0800
> >> Shenming Lu <lushenming@...wei.com> wrote:
> >>
> >>> To set up nested mode, drivers such as vfio_pci need to register a
> >>> handler to receive stage/level 1 faults from the IOMMU, but since
> >>> currently each device can only have one iommu dev fault handler,
> >>> and if stage 2 IOPF is already enabled (VFIO_IOMMU_ENABLE_IOPF),
> >>> we choose to update the registered handler (a consolidated one) via
> >>> flags (set FAULT_REPORT_NESTED_L1), and further deliver the received
> >>> stage 1 faults in the handler to the guest through a newly added
> >>> vfio_device_ops callback.
> >>
> >> Are there proposed in-kernel drivers that would use any of these
> >> symbols?
> >
> > I hope that such as Eric's SMMUv3 Nested Stage Setup series [1] can
> > use these symbols to consolidate the two page fault handlers into one.
> >
> > [1] https://patchwork.kernel.org/project/kvm/cover/20210411114659.15051-1-eric.auger@redhat.com/
> >
> >>
> >>> Signed-off-by: Shenming Lu <lushenming@...wei.com>
> >>> ---
> >>> drivers/vfio/vfio.c | 81 +++++++++++++++++++++++++++++++++
> >>> drivers/vfio/vfio_iommu_type1.c | 49 +++++++++++++++++++-
> >>> include/linux/vfio.h | 12 +++++
> >>> 3 files changed, 141 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> >>> index 44c8dfabf7de..4245f15914bf 100644
> >>> --- a/drivers/vfio/vfio.c
> >>> +++ b/drivers/vfio/vfio.c
> >>> @@ -2356,6 +2356,87 @@ struct iommu_domain *vfio_group_iommu_domain(struct vfio_group *group)
> >>> }
> >>> EXPORT_SYMBOL_GPL(vfio_group_iommu_domain);
> >>>
> >>> +/*
> >>> + * Register/Update the VFIO IOPF handler to receive
> >>> + * nested stage/level 1 faults.
> >>> + */
> >>> +int vfio_iommu_dev_fault_handler_register_nested(struct device *dev)
> >>> +{
> >>> + struct vfio_container *container;
> >>> + struct vfio_group *group;
> >>> + struct vfio_iommu_driver *driver;
> >>> + int ret;
> >>> +
> >>> + if (!dev)
> >>> + return -EINVAL;
> >>> +
> >>> + group = vfio_group_get_from_dev(dev);
> >>> + if (!group)
> >>> + return -ENODEV;
> >>> +
> >>> + ret = vfio_group_add_container_user(group);
> >>> + if (ret)
> >>> + goto out;
> >>> +
> >>> + container = group->container;
> >>> + driver = container->iommu_driver;
> >>> + if (likely(driver && driver->ops->register_handler))
> >>> + ret = driver->ops->register_handler(container->iommu_data, dev);
> >>> + else
> >>> + ret = -ENOTTY;
> >>> +
> >>> + vfio_group_try_dissolve_container(group);
> >>> +
> >>> +out:
> >>> + vfio_group_put(group);
> >>> + return ret;
> >>> +}
> >>> +EXPORT_SYMBOL_GPL(vfio_iommu_dev_fault_handler_register_nested);
> >>> +
> >>> +int vfio_iommu_dev_fault_handler_unregister_nested(struct device *dev)
> >>> +{
> >>> + struct vfio_container *container;
> >>> + struct vfio_group *group;
> >>> + struct vfio_iommu_driver *driver;
> >>> + int ret;
> >>> +
> >>> + if (!dev)
> >>> + return -EINVAL;
> >>> +
> >>> + group = vfio_group_get_from_dev(dev);
> >>> + if (!group)
> >>> + return -ENODEV;
> >>> +
> >>> + ret = vfio_group_add_container_user(group);
> >>> + if (ret)
> >>> + goto out;
> >>> +
> >>> + container = group->container;
> >>> + driver = container->iommu_driver;
> >>> + if (likely(driver && driver->ops->unregister_handler))
> >>> + ret = driver->ops->unregister_handler(container->iommu_data, dev);
> >>> + else
> >>> + ret = -ENOTTY;
> >>> +
> >>> + vfio_group_try_dissolve_container(group);
> >>> +
> >>> +out:
> >>> + vfio_group_put(group);
> >>> + return ret;
> >>> +}
> >>> +EXPORT_SYMBOL_GPL(vfio_iommu_dev_fault_handler_unregister_nested);
> >>> +
> >>> +int vfio_transfer_iommu_fault(struct device *dev, struct iommu_fault *fault)
> >>> +{
> >>> + struct vfio_device *device = dev_get_drvdata(dev);
> >>> +
> >>> + if (unlikely(!device->ops->transfer))
> >>> + return -EOPNOTSUPP;
> >>> +
> >>> + return device->ops->transfer(device->device_data, fault);
> >>> +}
> >>> +EXPORT_SYMBOL_GPL(vfio_transfer_iommu_fault);
> >>> +
> >>> /**
> >>> * Module/class support
> >>> */
> >>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> >>> index ba2b5a1cf6e9..9d1adeddb303 100644
> >>> --- a/drivers/vfio/vfio_iommu_type1.c
> >>> +++ b/drivers/vfio/vfio_iommu_type1.c
> >>> @@ -3821,13 +3821,32 @@ static int vfio_iommu_type1_dma_map_iopf(struct iommu_fault *fault, void *data)
> >>> struct vfio_batch batch;
> >>> struct vfio_range *range;
> >>> dma_addr_t iova = ALIGN_DOWN(fault->prm.addr, PAGE_SIZE);
> >>> - int access_flags = 0;
> >>> + int access_flags = 0, nested;
> >>> size_t premap_len, map_len, mapped_len = 0;
> >>> unsigned long bit_offset, vaddr, pfn, i, npages;
> >>> int ret;
> >>> enum iommu_page_response_code status = IOMMU_PAGE_RESP_INVALID;
> >>> struct iommu_page_response resp = {0};
> >>>
> >>> + if (vfio_dev_domian_nested(dev, &nested))
> >>> + return -ENODEV;
> >>> +
> >>> + /*
> >>> + * When configured in nested mode, further deliver the
> >>> + * stage/level 1 faults to the guest.
> >>> + */
> >>> + if (nested) {
> >>> + bool l2;
> >>> +
> >>> + if (fault->type == IOMMU_FAULT_PAGE_REQ)
> >>> + l2 = fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_L2;
> >>> + if (fault->type == IOMMU_FAULT_DMA_UNRECOV)
> >>> + l2 = fault->event.flags & IOMMU_FAULT_UNRECOV_L2;
> >>> +
> >>> + if (!l2)
> >>> + return vfio_transfer_iommu_fault(dev, fault);
> >>> + }
> >>> +
> >>> if (fault->type != IOMMU_FAULT_PAGE_REQ)
> >>> return -EOPNOTSUPP;
> >>>
> >>> @@ -4201,6 +4220,32 @@ static void vfio_iommu_type1_notify(void *iommu_data,
> >>> wake_up_all(&iommu->vaddr_wait);
> >>> }
> >>>
> >>> +static int vfio_iommu_type1_register_handler(void *iommu_data,
> >>> + struct device *dev)
> >>> +{
> >>> + struct vfio_iommu *iommu = iommu_data;
> >>> +
> >>> + if (iommu->iopf_enabled)
> >>> + return iommu_update_device_fault_handler(dev, ~0,
> >>> + FAULT_REPORT_NESTED_L1);
> >>> + else
> >>> + return iommu_register_device_fault_handler(dev,
> >>> + vfio_iommu_type1_dma_map_iopf,
> >>> + FAULT_REPORT_NESTED_L1, dev);
> >>> +}
> >>> +
> >>> +static int vfio_iommu_type1_unregister_handler(void *iommu_data,
> >>> + struct device *dev)
> >>> +{
> >>> + struct vfio_iommu *iommu = iommu_data;
> >>> +
> >>> + if (iommu->iopf_enabled)
> >>> + return iommu_update_device_fault_handler(dev,
> >>> + ~FAULT_REPORT_NESTED_L1, 0);
> >>> + else
> >>> + return iommu_unregister_device_fault_handler(dev);
> >>> +}
> >>
> >>
> >> The path through vfio to register this is pretty ugly, but I don't see
> >> any reason for the the update interfaces here, the previously
> >> registered handler just changes its behavior.
> >
> > Yeah, this seems not an elegant way...
> >
> > If IOPF(L2) enabled, the fault handler has already been registered, so for
> > nested mode setup, we only need to change the flags of the handler in the
> > IOMMU driver to receive L1 faults.
> > (assume that L1 IOPF is configured after L2 IOPF)
> >
> > Currently each device can only have one iommu dev fault handler, and L1
> > and L2 IOPF are configured separately in nested mode, I am also wondering
> > that is there a better solution for this.
I haven't fully read all the references, but who imposes the fact that
there's only one fault handler per device? If type1 could register one
handler and the vfio-pci bus driver another for the other level, would
we need this path through vfio-core?
> Let me simply add, maybe there is another way for this:
> Would it be better to set host IOPF enabled (L2 faults) in the VFIO_IOMMU_MAP_DMA
> ioctl (no need to add a new ioctl, and we can specify whether this mapping is IOPF
> available or statically pinned), and set guest IOPF enabled (L1 faults) in the
> VFIO_IOMMU_SET_PASID_TABLE (from Eric's series) ioctl?
> And we have no requirement for the sequence of these two ioctls. The first called
> one will register the handler, and the later one will just update the handler...
This is looking more and more like it belongs with the IOASID work. I
think Eric has shifted his focus there too. Thanks,
Alex
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