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From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: Auger Eric <eric.auger@redhat.com>
Cc: jacob.jun.pan@linux.intel.com, kevin.tian@intel.com,
	yi.l.liu@intel.com, ashok.raj@intel.com, kvm@vger.kernel.org,
	joro@8bytes.org, will.deacon@arm.com,
	linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	marc.zyngier@arm.com,
	Alex Williamson <alex.williamson@redhat.com>,
	vincent.stehle@arm.com, robin.murphy@arm.com,
	kvmarm@lists.cs.columbia.edu, eric.auger.pro@gmail.com
Subject: Re: [PATCH v8 26/29] vfio-pci: Register an iommu fault handler
Date: Wed, 5 Jun 2019 15:45:53 -0700
Message-ID: <20190605154553.0d00ad8d@jacob-builder> (raw)
In-Reply-To: <10dd60d9-4af0-c0eb-08c9-a0db7ee1925e@redhat.com>

On Tue, 4 Jun 2019 18:11:08 +0200
Auger Eric <eric.auger@redhat.com> wrote:

> Hi Alex,
> 
> On 6/4/19 12:31 AM, Alex Williamson wrote:
> > On Sun, 26 May 2019 18:10:01 +0200
> > Eric Auger <eric.auger@redhat.com> wrote:
> >   
> >> This patch registers a fault handler which records faults in
> >> a circular buffer and then signals an eventfd. This buffer is
> >> exposed within the fault region.
> >>
> >> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> >>
> >> ---
> >>
> >> v3 -> v4:
> >> - move iommu_unregister_device_fault_handler to vfio_pci_release
> >> ---
> >>  drivers/vfio/pci/vfio_pci.c         | 49
> >> +++++++++++++++++++++++++++++ drivers/vfio/pci/vfio_pci_private.h
> >> |  1 + 2 files changed, 50 insertions(+)
> >>
> >> diff --git a/drivers/vfio/pci/vfio_pci.c
> >> b/drivers/vfio/pci/vfio_pci.c index f75f61127277..520999994ba8
> >> 100644 --- a/drivers/vfio/pci/vfio_pci.c
> >> +++ b/drivers/vfio/pci/vfio_pci.c
> >> @@ -30,6 +30,7 @@
> >>  #include <linux/vfio.h>
> >>  #include <linux/vgaarb.h>
> >>  #include <linux/nospec.h>
> >> +#include <linux/circ_buf.h>
> >>  
> >>  #include "vfio_pci_private.h"
> >>  
> >> @@ -296,6 +297,46 @@ static const struct vfio_pci_regops
> >> vfio_pci_fault_prod_regops = { .add_capability =
> >> vfio_pci_fault_prod_add_capability, };
> >>  
> >> +int vfio_pci_iommu_dev_fault_handler(struct iommu_fault_event
> >> *evt, void *data) +{
> >> +	struct vfio_pci_device *vdev = (struct vfio_pci_device *)
> >> data;
> >> +	struct vfio_region_fault_prod *prod_region =
> >> +		(struct vfio_region_fault_prod
> >> *)vdev->fault_pages;
> >> +	struct vfio_region_fault_cons *cons_region =
> >> +		(struct vfio_region_fault_cons
> >> *)(vdev->fault_pages + 2 * PAGE_SIZE);
> >> +	struct iommu_fault *new =
> >> +		(struct iommu_fault *)(vdev->fault_pages +
> >> prod_region->offset +
> >> +			prod_region->prod *
> >> prod_region->entry_size);
> >> +	int prod, cons, size;
> >> +
> >> +	mutex_lock(&vdev->fault_queue_lock);
> >> +
> >> +	if (!vdev->fault_abi)
> >> +		goto unlock;
> >> +
> >> +	prod = prod_region->prod;
> >> +	cons = cons_region->cons;
> >> +	size = prod_region->nb_entries;
> >> +
> >> +	if (CIRC_SPACE(prod, cons, size) < 1)
> >> +		goto unlock;
> >> +
> >> +	*new = evt->fault;
> >> +	prod = (prod + 1) % size;
> >> +	prod_region->prod = prod;
> >> +	mutex_unlock(&vdev->fault_queue_lock);
> >> +
> >> +	mutex_lock(&vdev->igate);
> >> +	if (vdev->dma_fault_trigger)
> >> +		eventfd_signal(vdev->dma_fault_trigger, 1);
> >> +	mutex_unlock(&vdev->igate);
> >> +	return 0;
> >> +
> >> +unlock:
> >> +	mutex_unlock(&vdev->fault_queue_lock);
> >> +	return -EINVAL;
> >> +}
> >> +
> >>  static int vfio_pci_init_fault_region(struct vfio_pci_device
> >> *vdev) {
> >>  	struct vfio_region_fault_prod *header;
> >> @@ -328,6 +369,13 @@ static int vfio_pci_init_fault_region(struct
> >> vfio_pci_device *vdev) header = (struct vfio_region_fault_prod
> >> *)vdev->fault_pages; header->version = -1;
> >>  	header->offset = PAGE_SIZE;
> >> +
> >> +	ret =
> >> iommu_register_device_fault_handler(&vdev->pdev->dev,
> >> +
> >> vfio_pci_iommu_dev_fault_handler,
> >> +					vdev);
> >> +	if (ret)
> >> +		goto out;
> >> +
> >>  	return 0;
> >>  out:
> >>  	kfree(vdev->fault_pages);
> >> @@ -570,6 +618,7 @@ static void vfio_pci_release(void *device_data)
> >>  	if (!(--vdev->refcnt)) {
> >>  		vfio_spapr_pci_eeh_release(vdev->pdev);
> >>  		vfio_pci_disable(vdev);
> >> +
> >> iommu_unregister_device_fault_handler(&vdev->pdev->dev);  
> > 
> > 
> > But this can fail if there are pending faults which leaves a device
> > reference and then the system is broken :(  
> This series only features unrecoverable errors and for those the
> unregistration cannot fail. Now unrecoverable errors were added I
> admit this is confusing. We need to sort this out or clean the
> dependencies.
As Alex pointed out in 4/29, we can make
iommu_unregister_device_fault_handler() never fail and clean up all the
pending faults in the host IOMMU belong to that device. But the problem
is that if a fault, such as PRQ, has already been injected into the
guest, the page response may come back after handler is unregistered
and registered again. We need a way to reject such page response belong
to the previous life of the handler. Perhaps a sync call to the guest
with your fault queue eventfd? I am not sure.

Jacob
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  reply index

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-26 16:09 [PATCH v8 00/29] SMMUv3 Nested Stage Setup Eric Auger
2019-05-26 16:09 ` [PATCH v8 01/29] driver core: Add per device iommu param Eric Auger
2019-05-26 16:09 ` [PATCH v8 02/29] iommu: Introduce device fault data Eric Auger
2019-05-26 16:09 ` [PATCH v8 03/29] iommu: Introduce device fault report API Eric Auger
2019-05-26 16:09 ` [PATCH v8 04/29] iommu: Add recoverable fault reporting Eric Auger
2019-06-03 22:31   ` Alex Williamson
2019-06-04 15:48     ` Jacob Pan
2019-05-26 16:09 ` [PATCH v8 05/29] iommu: Add a timeout parameter for PRQ response Eric Auger
2019-06-03 22:32   ` Alex Williamson
2019-06-04 10:52     ` Jean-Philippe Brucker
2019-06-04 15:50       ` Jacob Pan
2019-05-26 16:09 ` [PATCH v8 06/29] trace/iommu: Add sva trace events Eric Auger
2019-05-26 16:09 ` [PATCH v8 07/29] iommu: Use device fault trace event Eric Auger
2019-05-26 16:09 ` [PATCH v8 08/29] iommu: Introduce attach/detach_pasid_table API Eric Auger
2019-05-26 16:09 ` [PATCH v8 09/29] iommu: Introduce cache_invalidate API Eric Auger
2019-05-26 16:09 ` [PATCH v8 10/29] iommu: Introduce bind/unbind_guest_msi Eric Auger
2019-05-26 16:09 ` [PATCH v8 11/29] iommu/arm-smmu-v3: Maintain a SID->device structure Eric Auger
2019-05-26 16:09 ` [PATCH v8 12/29] iommu/smmuv3: Dynamically allocate s1_cfg and s2_cfg Eric Auger
2019-05-26 16:09 ` [PATCH v8 13/29] iommu/smmuv3: Get prepared for nested stage support Eric Auger
2019-05-26 16:09 ` [PATCH v8 14/29] iommu/smmuv3: Implement attach/detach_pasid_table Eric Auger
2019-05-26 16:09 ` [PATCH v8 15/29] iommu/smmuv3: Introduce __arm_smmu_tlb_inv_asid/s1_range_nosync Eric Auger
2019-05-26 16:09 ` [PATCH v8 16/29] iommu/smmuv3: Implement cache_invalidate Eric Auger
2019-05-26 16:09 ` [PATCH v8 17/29] dma-iommu: Implement NESTED_MSI cookie Eric Auger
2019-05-26 16:09 ` [PATCH v8 18/29] iommu/smmuv3: Nested mode single MSI doorbell per domain enforcement Eric Auger
2019-05-26 16:09 ` [PATCH v8 19/29] iommu/smmuv3: Enforce incompatibility between nested mode and HW MSI regions Eric Auger
2019-05-26 16:09 ` [PATCH v8 20/29] iommu/smmuv3: Implement bind/unbind_guest_msi Eric Auger
2019-05-26 16:09 ` [PATCH v8 21/29] iommu/smmuv3: Report non recoverable faults Eric Auger
2019-05-26 16:09 ` [PATCH v8 22/29] vfio: VFIO_IOMMU_ATTACH/DETACH_PASID_TABLE Eric Auger
2019-06-03 22:32   ` Alex Williamson
2019-05-26 16:09 ` [PATCH v8 23/29] vfio: VFIO_IOMMU_CACHE_INVALIDATE Eric Auger
2019-06-14 12:38   ` Liu, Yi L
2019-06-14 13:17     ` Auger Eric
2019-05-26 16:09 ` [PATCH v8 24/29] vfio: VFIO_IOMMU_BIND/UNBIND_MSI Eric Auger
2019-06-03 22:32   ` Alex Williamson
2019-06-07  8:30     ` Auger Eric
2019-05-26 16:10 ` [PATCH v8 25/29] vfio-pci: Add a new VFIO_REGION_TYPE_NESTED region type Eric Auger
2019-06-03 22:31   ` Alex Williamson
2019-06-07  8:28     ` Auger Eric
2019-06-07 12:47       ` Jean-Philippe Brucker
2019-06-07 16:29       ` Alex Williamson
2019-05-26 16:10 ` [PATCH v8 26/29] vfio-pci: Register an iommu fault handler Eric Auger
2019-06-03 22:31   ` Alex Williamson
2019-06-04 16:11     ` Auger Eric
2019-06-05 22:45       ` Jacob Pan [this message]
2019-06-06 18:54         ` Jean-Philippe Brucker
2019-06-06 20:29           ` Jacob Pan
2019-06-07  7:02             ` Auger Eric
2019-06-07 10:28             ` Jean-Philippe Brucker
2019-06-07 17:43               ` Jacob Pan
2019-06-10 12:45                 ` Jean-Philippe Brucker
2019-06-10 21:31                   ` Jacob Pan
2019-06-11 13:14                     ` Jean-Philippe Brucker
2019-06-12 18:53                       ` Jacob Pan
2019-06-18 14:04                         ` Jean-Philippe Brucker
2019-06-19  0:19                           ` Jacob Pan
2019-06-19 11:44                             ` Jean-Philippe Brucker
2019-07-11 13:07                           ` Auger Eric
2019-06-07 12:48   ` Jean-Philippe Brucker
2019-06-07 14:18     ` Auger Eric
2019-05-26 16:10 ` [PATCH v8 27/29] vfio_pci: Allow to mmap the fault queue Eric Auger
2019-05-26 16:10 ` [PATCH v8 28/29] vfio-pci: Add VFIO_PCI_DMA_FAULT_IRQ_INDEX Eric Auger
2019-06-03 22:31   ` Alex Williamson
2019-06-04 16:11     ` Auger Eric
2019-05-26 16:10 ` [PATCH v8 29/29] vfio: Document nested stage control Eric Auger

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