From: Baolu Lu <baolu.lu@linux.intel.com>
To: "Liu, Jingqi" <jingqi.liu@intel.com>,
Jason Gunthorpe <jgg@ziepe.ca>, Kevin Tian <kevin.tian@intel.com>,
Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Alex Williamson <alex.williamson@redhat.com>,
Nicolin Chen <nicolinc@nvidia.com>
Cc: baolu.lu@linux.intel.com, iommu@lists.linux.dev,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Jason Gunthorpe <jgg@nvidia.com>
Subject: Re: [PATCH 1/2] iommu: Prevent RESV_DIRECT devices from blocking domains
Date: Tue, 13 Jun 2023 11:14:30 +0800 [thread overview]
Message-ID: <69f50ced-e806-717a-0c74-a4cfa58600fa@linux.intel.com> (raw)
In-Reply-To: <8cc1d69e-f86d-fd04-7737-914d967dc0f5@intel.com>
On 6/12/23 4:28 PM, Liu, Jingqi wrote:
> On 6/7/2023 11:51 AM, Lu Baolu wrote:
>> The IOMMU_RESV_DIRECT flag indicates that a memory region must be mapped
>> 1:1 at all times. This means that the region must always be accessible to
>> the device, even if the device is attached to a blocking domain. This is
>> equal to saying that IOMMU_RESV_DIRECT flag prevents devices from being
>> attached to blocking domains.
>>
>> This also implies that devices that implement RESV_DIRECT regions will be
>> prevented from being assigned to user space since taking the DMA
>> ownership
>> immediately switches to a blocking domain.
>>
>> The rule of preventing devices with the IOMMU_RESV_DIRECT regions from
>> being assigned to user space has existed in the Intel IOMMU driver for
>> a long time. Now, this rule is being lifted up to a general core rule,
>> as other architectures like AMD and ARM also have RMRR-like reserved
>> regions. This has been discussed in the community mailing list and refer
>> to below link for more details.
>>
>> Other places using unmanaged domains for kernel DMA must follow the
>> iommu_get_resv_regions() and setup IOMMU_RESV_DIRECT - we do not restrict
>> them in the core code.
>>
>> Cc: Robin Murphy <robin.murphy@arm.com>
>> Cc: Alex Williamson <alex.williamson@redhat.com>
>> Cc: Kevin Tian <kevin.tian@intel.com>
>> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
>> Link:
>> https://lore.kernel.org/linux-iommu/BN9PR11MB5276E84229B5BD952D78E9598C639@BN9PR11MB5276.namprd11.prod.outlook.com
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> ---
>> include/linux/iommu.h | 2 ++
>> drivers/iommu/iommu.c | 39 +++++++++++++++++++++++++++++----------
>> 2 files changed, 31 insertions(+), 10 deletions(-)
>>
>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>> index d31642596675..fd18019ac951 100644
>> --- a/include/linux/iommu.h
>> +++ b/include/linux/iommu.h
>> @@ -409,6 +409,7 @@ struct iommu_fault_param {
>> * @priv: IOMMU Driver private data
>> * @max_pasids: number of PASIDs this device can consume
>> * @attach_deferred: the dma domain attachment is deferred
>> + * @requires_direct: The driver requested IOMMU_RESV_DIRECT
>> *
>> * TODO: migrate other per device data pointers under
>> iommu_dev_data, e.g.
>> * struct iommu_group *iommu_group;
>> @@ -422,6 +423,7 @@ struct dev_iommu {
>> void *priv;
>> u32 max_pasids;
>> u32 attach_deferred:1;
>> + u32 requires_direct:1;
>> };
>> int iommu_device_register(struct iommu_device *iommu,
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index 9e0228ef612b..e59de7852067 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -959,12 +959,7 @@ static int
>> iommu_create_device_direct_mappings(struct iommu_domain *domain,
>> unsigned long pg_size;
>> int ret = 0;
>> - if (!iommu_is_dma_domain(domain))
>> - return 0;
>> -
>> - BUG_ON(!domain->pgsize_bitmap);
>> -
>> - pg_size = 1UL << __ffs(domain->pgsize_bitmap);
>> + pg_size = domain->pgsize_bitmap ? 1UL <<
>> __ffs(domain->pgsize_bitmap) : 0;
> Would it be better to add the following check here?
> if (WARN_ON(!pg_size))
> return -EINVAL;
>
> Instead of checking latter in the loop as follows.
> if (WARN_ON_ONCE(!pg_size)) {
> ret = -EINVAL;
> goto out;
> }
I am afraid no. Only the paging domains need a valid pg_size. That's the
reason why I put it after the iommu_is_dma_domain() check. The previous
code has the same behavior too.
Best regards,
baolu
next prev parent reply other threads:[~2023-06-13 3:15 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-07 3:51 [PATCH 0/2] Prevent RESV_DIRECT devices from user assignment Lu Baolu
2023-06-07 3:51 ` [PATCH 1/2] iommu: Prevent RESV_DIRECT devices from blocking domains Lu Baolu
2023-06-12 8:28 ` Liu, Jingqi
2023-06-13 3:14 ` Baolu Lu [this message]
2023-06-27 7:54 ` Tian, Kevin
2023-06-27 8:01 ` Baolu Lu
2023-06-27 8:15 ` Tian, Kevin
2023-06-27 8:21 ` Baolu Lu
2023-06-27 15:47 ` Jason Gunthorpe
2023-06-19 13:33 ` Robin Murphy
2023-06-19 13:41 ` Jason Gunthorpe
2023-06-19 14:20 ` Robin Murphy
2023-06-19 15:30 ` Jason Gunthorpe
2023-06-27 8:10 ` Tian, Kevin
2023-06-27 15:49 ` Jason Gunthorpe
2023-06-07 3:51 ` [PATCH 2/2] iommu/vt-d: Remove rmrr check in domain attaching device path Lu Baolu
2023-06-23 16:49 ` Jason Gunthorpe
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