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iommufd: Change the order of MSI setup

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Eric points out this is wrong for the rare case of someone using
allow_unsafe_interrupts on ARM. We always have to setup the MSI window in
the domain if the iommu driver asks for it.

Move the iommu_get_msi_cookie() setup to the top of the function and
always do it, regardless of the security mode. Add checks to
iommufd_device_setup_msi() to ensure the driver is not doing something
incomprehensible. No current driver will set both a HW and SW MSI window,
or have more than one SW MSI window.

Fixes: e8d5721003 ("iommufd: Add kAPI toward external drivers for physical devices")
Link: https://lore.kernel.org/r/3-v1-0362a1a1c034+98-iommufd_fixes1_jgg@nvidia.com
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reported-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
This commit is contained in:
Jason Gunthorpe 2022-12-07 16:44:43 -04:00
parent a26fa39206
commit d6c55c0a20
2 changed files with 39 additions and 41 deletions
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56
drivers/iommu/iommufd/device.c
View file

@ -139,19 +139,11 @@ static int iommufd_device_setup_msi(struct iommufd_device *idev,
int rc;
/*
* IOMMU_CAP_INTR_REMAP means that the platform is isolating MSI, and it
* creates the MSI window by default in the iommu domain. Nothing
* further to do.
*/
if (device_iommu_capable(idev->dev, IOMMU_CAP_INTR_REMAP))
return 0;
/*
* On ARM systems that set the global IRQ_DOMAIN_FLAG_MSI_REMAP every
* allocated iommu_domain will block interrupts by default and this
* special flow is needed to turn them back on. iommu_dma_prepare_msi()
* will install pages into our domain after request_irq() to make this
* work.
* If the IOMMU driver gives a IOMMU_RESV_SW_MSI then it is asking us to
* call iommu_get_msi_cookie() on its behalf. This is necessary to setup
* the MSI window so iommu_dma_prepare_msi() can install pages into our
* domain after request_irq(). If it is not done interrupts will not
* work on this domain.
*
* FIXME: This is conceptually broken for iommufd since we want to allow
* userspace to change the domains, eg switch from an identity IOAS to a
@ -159,33 +151,35 @@ static int iommufd_device_setup_msi(struct iommufd_device *idev,
* matches what the IRQ layer actually expects in a newly created
* domain.
*/
if (irq_domain_check_msi_remap()) {
if (WARN_ON(!sw_msi_start))
return -EPERM;
if (sw_msi_start != PHYS_ADDR_MAX && !hwpt->msi_cookie) {
rc = iommu_get_msi_cookie(hwpt->domain, sw_msi_start);
if (rc)
return rc;
/*
* iommu_get_msi_cookie() can only be called once per domain,
* it returns -EBUSY on later calls.
*/
if (hwpt->msi_cookie)
return 0;
rc = iommu_get_msi_cookie(hwpt->domain, sw_msi_start);
if (rc)
return rc;
hwpt->msi_cookie = true;
return 0;
}
/*
* Otherwise the platform has a MSI window that is not isolated. For
* historical compat with VFIO allow a module parameter to ignore the
* insecurity.
* For historical compat with VFIO the insecure interrupt path is
* allowed if the module parameter is set. Insecure means that a MemWr
* operation from the device (eg a simple DMA) cannot trigger an
* interrupt outside this iommufd context.
*/
if (!allow_unsafe_interrupts)
return -EPERM;
if (!device_iommu_capable(idev->dev, IOMMU_CAP_INTR_REMAP) &&
!irq_domain_check_msi_remap()) {
if (!allow_unsafe_interrupts)
return -EPERM;
dev_warn(
idev->dev,
"MSI interrupt window cannot be isolated by the IOMMU, this platform is insecure. Use the \"allow_unsafe_interrupts\" module parameter to override\n");
dev_warn(
idev->dev,
"MSI interrupts are not secure, they cannot be isolated by the platform. "
"Check that platform features like interrupt remapping are enabled. "
"Use the \"allow_unsafe_interrupts\" module parameter to override\n");
}
return 0;
}
@ -203,7 +197,7 @@ static bool iommufd_hw_pagetable_has_group(struct iommufd_hw_pagetable *hwpt,
static int iommufd_device_do_attach(struct iommufd_device *idev,
struct iommufd_hw_pagetable *hwpt)
{
phys_addr_t sw_msi_start = 0;
phys_addr_t sw_msi_start = PHYS_ADDR_MAX;
int rc;
mutex_lock(&hwpt->devices_lock);

24
drivers/iommu/iommufd/io_pagetable.c
View file

@ -1170,6 +1170,8 @@ int iopt_table_enforce_group_resv_regions(struct io_pagetable *iopt,
struct iommu_resv_region *resv;
struct iommu_resv_region *tmp;
LIST_HEAD(group_resv_regions);
unsigned int num_hw_msi = 0;
unsigned int num_sw_msi = 0;
int rc;
down_write(&iopt->iova_rwsem);
@ -1181,23 +1183,25 @@ int iopt_table_enforce_group_resv_regions(struct io_pagetable *iopt,
if (resv->type == IOMMU_RESV_DIRECT_RELAXABLE)
continue;
/*
* The presence of any 'real' MSI regions should take precedence
* over the software-managed one if the IOMMU driver happens to
* advertise both types.
*/
if (sw_msi_start && resv->type == IOMMU_RESV_MSI) {
*sw_msi_start = 0;
sw_msi_start = NULL;
}
if (sw_msi_start && resv->type == IOMMU_RESV_SW_MSI)
if (sw_msi_start && resv->type == IOMMU_RESV_MSI)
num_hw_msi++;
if (sw_msi_start && resv->type == IOMMU_RESV_SW_MSI) {
*sw_msi_start = resv->start;
num_sw_msi++;
}
rc = iopt_reserve_iova(iopt, resv->start,
resv->length - 1 + resv->start, device);
if (rc)
goto out_reserved;
}
/* Drivers must offer sane combinations of regions */
if (WARN_ON(num_sw_msi && num_hw_msi) || WARN_ON(num_sw_msi > 1)) {
rc = -EINVAL;
goto out_reserved;
}
rc = 0;
goto out_free_resv;