Re: [PATCH v4 3/6] iommu/sva: Stop using ioasid_set for SVA
From: Baolu Lu
Date: Thu Mar 02 2023 - 21:25:51 EST
On 3/3/23 1:17 AM, Jacob Pan wrote:
Hi Baolu,
On Thu, 2 Mar 2023 21:01:42 +0800, Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
wrote:
On 2023/3/2 7:56, Jacob Pan wrote:
From: Jason Gunthorpe <jgg@xxxxxxxxxx>
Instead SVA drivers can use a simple global IDA to allocate PASIDs for
each mm_struct.
Future work would be to allow drivers using the SVA APIs to reserve
global PASIDs from this IDA for their internal use, eg with the DMA API
PASID support.
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
---
v4:
- Keep GFP_ATOMIC flag for PASID allocation, will changed to
GFP_KERNEL in a separate patch.
---
drivers/iommu/iommu-sva.c | 62 ++++++++++-----------------------------
drivers/iommu/iommu-sva.h | 3 --
2 files changed, 15 insertions(+), 50 deletions(-)
diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
index 376b2a9e2543..297852ae5e7c 100644
--- a/drivers/iommu/iommu-sva.c
+++ b/drivers/iommu/iommu-sva.c
@@ -9,26 +9,13 @@
#include "iommu-sva.h"
static DEFINE_MUTEX(iommu_sva_lock);
-static DECLARE_IOASID_SET(iommu_sva_pasid);
+static DEFINE_IDA(iommu_global_pasid_ida);
-/**
- * iommu_sva_alloc_pasid - Allocate a PASID for the mm
- * @mm: the mm
- * @min: minimum PASID value (inclusive)
- * @max: maximum PASID value (inclusive)
- *
- * Try to allocate a PASID for this mm, or take a reference to the
existing one
- * provided it fits within the [@min, @max] range. On success the
PASID is
- * available in mm->pasid and will be available for the lifetime of
the mm.
- *
- * Returns 0 on success and < 0 on error.
- */
-int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t
max) +static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t
min, ioasid_t max) {
- int ret = 0;
- ioasid_t pasid;
+ int ret;
- if (min == INVALID_IOASID || max == INVALID_IOASID ||
+ if (min == IOMMU_PASID_INVALID || max == IOMMU_PASID_INVALID ||
min == 0 || max < min)
It's irrelevant to this patch. Just out of curiosity, why do we need to
exclude PASID 0 here? I just had a quick look at PCI spec section 6.20.
The spec does not state that PASID 0 is invalid.
my understanding is that ARM reserves PASID0, unlike VT-d where RID_PASID
is programmable.
I suppose the common thing is reserving some kind of special PASIDs.
return -EINVAL;
@@ -37,39 +24,20 @@ int iommu_sva_alloc_pasid(struct mm_struct *mm,
ioasid_t min, ioasid_t max) if (pasid_valid(mm->pasid)) {
if (mm->pasid < min || mm->pasid >= max)
ret = -EOVERFLOW;
+ else
+ ret = 0;
Nit:
If you didn't change "int ret = 0" to "int ret", we don't need above two
lines. Did I miss anything?
you are right
goto out;
}
- pasid = ioasid_alloc(&iommu_sva_pasid, min, max, mm);
- if (!pasid_valid(pasid))
- ret = -ENOMEM;
- else
- mm->pasid = ret;
+ ret = ida_alloc_range(&iommu_global_pasid_ida, min, max,
GFP_ATOMIC);
+ if (ret < min)
Nit:
ret < 0?
will do
ida_alloc_range() returns negative error number on failure.
+ goto out;
+ mm->pasid = ret;
+ ret = 0;
out:
mutex_unlock(&iommu_sva_lock);
return ret;
}
-EXPORT_SYMBOL_GPL(iommu_sva_alloc_pasid);
-
-/* ioasid_find getter() requires a void * argument */
-static bool __mmget_not_zero(void *mm)
-{
- return mmget_not_zero(mm);
-}
-
-/**
- * iommu_sva_find() - Find mm associated to the given PASID
- * @pasid: Process Address Space ID assigned to the mm
- *
- * On success a reference to the mm is taken, and must be released
with mmput().
- *
- * Returns the mm corresponding to this PASID, or an error if not
found.
- */
-struct mm_struct *iommu_sva_find(ioasid_t pasid)
-{
- return ioasid_find(&iommu_sva_pasid, pasid, __mmget_not_zero);
-}
-EXPORT_SYMBOL_GPL(iommu_sva_find);
Removing iommu_sva_find() has nothing to do with the intention of this
patch. Perhaps make it in a separated patch?
will do
/**
* iommu_sva_bind_device() - Bind a process address space to a device
@@ -241,8 +209,8 @@ iommu_sva_handle_iopf(struct iommu_fault *fault,
void *data)
void mm_pasid_drop(struct mm_struct *mm)
{
- if (pasid_valid(mm->pasid)) {
- ioasid_free(mm->pasid);
- mm->pasid = INVALID_IOASID;
- }
+ if (likely(!pasid_valid(mm->pasid)))
Why is this a likely?
most mm does not have a PASID, thus initialized with invalid ioasid during
fork. This function is called for every mm.
Make sense.
+ return;
+
+ ida_free(&iommu_global_pasid_ida, mm->pasid);
}
diff --git a/drivers/iommu/iommu-sva.h b/drivers/iommu/iommu-sva.h
index 7215a761b962..c22d0174ad61 100644
--- a/drivers/iommu/iommu-sva.h
+++ b/drivers/iommu/iommu-sva.h
@@ -8,9 +8,6 @@
#include <linux/ioasid.h>
#include <linux/mm_types.h>
-int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t
max); -struct mm_struct *iommu_sva_find(ioasid_t pasid);
-
/* I/O Page fault */
struct device;
struct iommu_fault;
Best regards,
baolu
Thanks,
Jacob
Best regards,
baolu