Re: [PATCH v3 09/11] iommu: Make iommu_queue_iopf() more generic

Baolu Lu
2023-08-22T08:49:19Z

On 2023/8/22 1:11, Jason Gunthorpe wrote:
> On Fri, Aug 18, 2023 at 07:40:45AM +0800, Lu Baolu wrote:
>> This completely separates the IO page fault handling framework from the
>> SVA implementation. Previously, the SVA implementation was tightly coupled
>> with the IO page fault handling framework. This makes SVA a "customer" of
>> the IO page fault handling framework by converting domain's page fault
>> handler to handle a group of faults and calling it directly from
>> iommu_queue_iopf().
>>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> ---
>> include/linux/iommu.h | 5 +++--
>> drivers/iommu/iommu-sva.h | 8 --------
>> drivers/iommu/io-pgfault.c | 16 +++++++++++++---
>> drivers/iommu/iommu-sva.c | 14 ++++----------
>> drivers/iommu/iommu.c | 4 ++--
>> 5 files changed, 22 insertions(+), 25 deletions(-)
>>
>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>> index ff292eea9d31..cf1cb0bb46af 100644
>> --- a/include/linux/iommu.h
>> +++ b/include/linux/iommu.h
>> @@ -41,6 +41,7 @@ struct iommu_sva;
>> struct iommu_fault_event;
>> struct iommu_dma_cookie;
>> struct iopf_queue;
>> +struct iopf_group;
>>
>> #define IOMMU_FAULT_PERM_READ (1 << 0) /* read */
>> #define IOMMU_FAULT_PERM_WRITE (1 << 1) /* write */
>> @@ -175,8 +176,7 @@ struct iommu_domain {
>> unsigned long pgsize_bitmap; /* Bitmap of page sizes in use */
>> struct iommu_domain_geometry geometry;
>> struct iommu_dma_cookie *iova_cookie;
>> - enum iommu_page_response_code (*iopf_handler)(struct iommu_fault *fault,
>> - void *data);
>> + int (*iopf_handler)(struct iopf_group *group);
>> void *fault_data;
>> union {
>> struct {
>> @@ -526,6 +526,7 @@ struct iopf_group {
>> struct list_head faults;
>> struct work_struct work;
>> struct device *dev;
>> + void *data;
>> };
>>
>> int iommu_device_register(struct iommu_device *iommu,
>> diff --git a/drivers/iommu/iommu-sva.h b/drivers/iommu/iommu-sva.h
>> index 510a7df23fba..cf41e88fac17 100644
>> --- a/drivers/iommu/iommu-sva.h
>> +++ b/drivers/iommu/iommu-sva.h
>> @@ -22,8 +22,6 @@ int iopf_queue_flush_dev(struct device *dev);
>> struct iopf_queue *iopf_queue_alloc(const char *name);
>> void iopf_queue_free(struct iopf_queue *queue);
>> int iopf_queue_discard_partial(struct iopf_queue *queue);
>> -enum iommu_page_response_code
>> -iommu_sva_handle_iopf(struct iommu_fault *fault, void *data);
>> void iopf_free_group(struct iopf_group *group);
>> int iopf_queue_work(struct iopf_group *group, work_func_t func);
>> int iommu_sva_handle_iopf_group(struct iopf_group *group);
>> @@ -65,12 +63,6 @@ static inline int iopf_queue_discard_partial(struct iopf_queue *queue)
>> return -ENODEV;
>> }
>>
>> -static inline enum iommu_page_response_code
>> -iommu_sva_handle_iopf(struct iommu_fault *fault, void *data)
>> -{
>> - return IOMMU_PAGE_RESP_INVALID;
>> -}
>> -
>> static inline void iopf_free_group(struct iopf_group *group)
>> {
>> }
>> diff --git a/drivers/iommu/io-pgfault.c b/drivers/iommu/io-pgfault.c
>> index 00c2e447b740..a61c2aabd1b8 100644
>> --- a/drivers/iommu/io-pgfault.c
>> +++ b/drivers/iommu/io-pgfault.c
>> @@ -11,8 +11,6 @@
>> #include <linux/slab.h>
>> #include <linux/workqueue.h>
>>
>> -#include "iommu-sva.h"
>> -
>> /**
>> * struct iopf_queue - IO Page Fault queue
>> * @wq: the fault workqueue
>> @@ -93,6 +91,7 @@ int iommu_queue_iopf(struct iommu_fault *fault, struct device *dev)
>> {
>> int ret;
>> struct iopf_group *group;
>> + struct iommu_domain *domain;
>> struct iopf_fault *iopf, *next;
>> struct iommu_fault_param *iopf_param;
>> struct dev_iommu *param = dev->iommu;
>> @@ -124,6 +123,16 @@ int iommu_queue_iopf(struct iommu_fault *fault, struct device *dev)
>> return 0;
>> }
>>
>> + if (fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID)
>> + domain = iommu_get_domain_for_dev_pasid(dev, fault->prm.pasid, 0);
>> + else
>> + domain = iommu_get_domain_for_dev(dev);
>> +
>> + if (!domain || !domain->iopf_handler) {
>> + ret = -ENODEV;
>> + goto cleanup_partial;
>> + }
>> +
>> group = kzalloc(sizeof(*group), GFP_KERNEL);
>> if (!group) {
>> /*
>> @@ -137,6 +146,7 @@ int iommu_queue_iopf(struct iommu_fault *fault, struct device *dev)
>>
>> group->dev = dev;
>> group->last_fault.fault = *fault;
>> + group->data = domain->fault_data;
>> INIT_LIST_HEAD(&group->faults);
>> list_add(&group->last_fault.list, &group->faults);
>>
>> @@ -147,7 +157,7 @@ int iommu_queue_iopf(struct iommu_fault *fault, struct device *dev)
>> list_move(&iopf->list, &group->faults);
>> }
>>
>> - ret = iommu_sva_handle_iopf_group(group);
>> + ret = domain->iopf_handler(group);
>> if (ret)
>> iopf_free_group(group);
>>
>> diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
>> index df8734b6ec00..2811f34947ab 100644
>> --- a/drivers/iommu/iommu-sva.c
>> +++ b/drivers/iommu/iommu-sva.c
>> @@ -148,13 +148,14 @@ EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
>> /*
>> * I/O page fault handler for SVA
>> */
>> -enum iommu_page_response_code
>> +static enum iommu_page_response_code
>> iommu_sva_handle_iopf(struct iommu_fault *fault, void *data)
>> {
>> vm_fault_t ret;
>> struct vm_area_struct *vma;
>> - struct mm_struct *mm = data;
>> unsigned int access_flags = 0;
>> + struct iommu_domain *domain = data;
>> + struct mm_struct *mm = domain->mm;
>> unsigned int fault_flags = FAULT_FLAG_REMOTE;
>> struct iommu_fault_page_request *prm = &fault->prm;
>> enum iommu_page_response_code status = IOMMU_PAGE_RESP_INVALID;
>> @@ -231,23 +232,16 @@ static void iommu_sva_iopf_handler(struct work_struct *work)
>> {
>> struct iopf_fault *iopf;
>> struct iopf_group *group;
>> - struct iommu_domain *domain;
>> enum iommu_page_response_code status = IOMMU_PAGE_RESP_SUCCESS;
>>
>> group = container_of(work, struct iopf_group, work);
>> - domain = iommu_get_domain_for_dev_pasid(group->dev,
>> - group->last_fault.fault.prm.pasid, 0);
>> - if (!domain || !domain->iopf_handler)
>> - status = IOMMU_PAGE_RESP_INVALID;
>> -
>> list_for_each_entry(iopf, &group->faults, list) {
>> /*
>> * For the moment, errors are sticky: don't handle subsequent
>> * faults in the group if there is an error.
>> */
>> if (status == IOMMU_PAGE_RESP_SUCCESS)
>> - status = domain->iopf_handler(&iopf->fault,
>> - domain->fault_data);
>> + status = iommu_sva_handle_iopf(&iopf->fault, group->data);
>> }
>>
>> iommu_sva_complete_iopf(group->dev, &group->last_fault, status);
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index b280b9f4d8b4..9b622088c741 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -3395,8 +3395,8 @@ struct iommu_domain *iommu_sva_domain_alloc(struct device *dev,
>> domain->type = IOMMU_DOMAIN_SVA;
>> mmgrab(mm);
>> domain->mm = mm;
>> - domain->iopf_handler = iommu_sva_handle_iopf;
>> - domain->fault_data = mm;
>> + domain->iopf_handler = iommu_sva_handle_iopf_group;
>> + domain->fault_data = domain;
>
> Why fault_data? The domain handling the fault should be passed
> through naturally without relying on fault_data.
>
> eg make
>
> iommu_sva_handle_iopf(struct iommu_fault *fault, void *data)
>
> into
> iommu_sva_handle_iopf(struct iommu_fault *fault, struct iommu_domain *domain)

See your point now. I will remove "void *data" and move "domain" to
"group->domain".

>
> And delete domain->fault_data until we have some use for it.

Perhaps we will soon have a use for it.

In the iommufd case, the iommufd iopf handler has a need to retrieve the
hwpt pointer from a domain pointer, right? With the domain->fault_data
pointing to the hwpt, the iopf handler has no need to lookup it in the
critical path.

>
> The core code should be keeping track of the iommu_domain lifetime.

I added the debugging code in the next patch as you suggested.

Best regards,
baolu