From: Christoph Hellwig <hch@lst.de>
Split the iommu logic from iommu_dma_map_page into a separate helper.
This not only keeps the code neatly separated, but will also allow for
reuse in another caller.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
drivers/iommu/dma-iommu.c | 73 ++++++++++++++++++++++-----------------
1 file changed, 41 insertions(+), 32 deletions(-)
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index d3211a8d755e..d7684024c439 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1138,6 +1138,43 @@ void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
arch_sync_dma_for_device(sg_phys(sg), sg->length, dir);
}
+static phys_addr_t iommu_dma_map_swiotlb(struct device *dev, phys_addr_t phys,
+ size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+ struct iommu_domain *domain = iommu_get_dma_domain(dev);
+ struct iova_domain *iovad = &domain->iova_cookie->iovad;
+
+ if (!is_swiotlb_active(dev)) {
+ dev_warn_once(dev, "DMA bounce buffers are inactive, unable to map unaligned transaction.\n");
+ return (phys_addr_t)DMA_MAPPING_ERROR;
+ }
+
+ trace_swiotlb_bounced(dev, phys, size);
+
+ phys = swiotlb_tbl_map_single(dev, phys, size, iova_mask(iovad), dir,
+ attrs);
+
+ /*
+ * Untrusted devices should not see padding areas with random leftover
+ * kernel data, so zero the pre- and post-padding.
+ * swiotlb_tbl_map_single() has initialized the bounce buffer proper to
+ * the contents of the original memory buffer.
+ */
+ if (phys != (phys_addr_t)DMA_MAPPING_ERROR && dev_is_untrusted(dev)) {
+ size_t start, virt = (size_t)phys_to_virt(phys);
+
+ /* Pre-padding */
+ start = iova_align_down(iovad, virt);
+ memset((void *)start, 0, virt - start);
+
+ /* Post-padding */
+ start = virt + size;
+ memset((void *)start, 0, iova_align(iovad, start) - start);
+ }
+
+ return phys;
+}
+
dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
unsigned long offset, size_t size, enum dma_data_direction dir,
unsigned long attrs)
@@ -1151,42 +1188,14 @@ dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
dma_addr_t iova, dma_mask = dma_get_mask(dev);
/*
- * If both the physical buffer start address and size are
- * page aligned, we don't need to use a bounce page.
+ * If both the physical buffer start address and size are page aligned,
+ * we don't need to use a bounce page.
*/
if (dev_use_swiotlb(dev, size, dir) &&
iova_offset(iovad, phys | size)) {
- if (!is_swiotlb_active(dev)) {
- dev_warn_once(dev, "DMA bounce buffers are inactive, unable to map unaligned transaction.\n");
- return DMA_MAPPING_ERROR;
- }
-
- trace_swiotlb_bounced(dev, phys, size);
-
- phys = swiotlb_tbl_map_single(dev, phys, size,
- iova_mask(iovad), dir, attrs);
-
- if (phys == DMA_MAPPING_ERROR)
+ phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);
+ if (phys == (phys_addr_t)DMA_MAPPING_ERROR)
return DMA_MAPPING_ERROR;
-
- /*
- * Untrusted devices should not see padding areas with random
- * leftover kernel data, so zero the pre- and post-padding.
- * swiotlb_tbl_map_single() has initialized the bounce buffer
- * proper to the contents of the original memory buffer.
- */
- if (dev_is_untrusted(dev)) {
- size_t start, virt = (size_t)phys_to_virt(phys);
-
- /* Pre-padding */
- start = iova_align_down(iovad, virt);
- memset((void *)start, 0, virt - start);
-
- /* Post-padding */
- start = virt + size;
- memset((void *)start, 0,
- iova_align(iovad, start) - start);
- }
}
if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
--
2.49.0On 4/28/25 17:22, Leon Romanovsky wrote:
> From: Christoph Hellwig<hch@lst.de>
>
> Split the iommu logic from iommu_dma_map_page into a separate helper.
> This not only keeps the code neatly separated, but will also allow for
> reuse in another caller.
>
> Signed-off-by: Christoph Hellwig<hch@lst.de>
> Tested-by: Jens Axboe<axboe@kernel.dk>
> Reviewed-by: Luis Chamberlain<mcgrof@kernel.org>
> Signed-off-by: Leon Romanovsky<leonro@nvidia.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
with a nit below ...
> ---
> drivers/iommu/dma-iommu.c | 73 ++++++++++++++++++++++-----------------
> 1 file changed, 41 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index d3211a8d755e..d7684024c439 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -1138,6 +1138,43 @@ void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
> arch_sync_dma_for_device(sg_phys(sg), sg->length, dir);
> }
>
> +static phys_addr_t iommu_dma_map_swiotlb(struct device *dev, phys_addr_t phys,
> + size_t size, enum dma_data_direction dir, unsigned long attrs)
> +{
> + struct iommu_domain *domain = iommu_get_dma_domain(dev);
> + struct iova_domain *iovad = &domain->iova_cookie->iovad;
> +
> + if (!is_swiotlb_active(dev)) {
> + dev_warn_once(dev, "DMA bounce buffers are inactive, unable to map unaligned transaction.\n");
> + return (phys_addr_t)DMA_MAPPING_ERROR;
> + }
> +
> + trace_swiotlb_bounced(dev, phys, size);
> +
> + phys = swiotlb_tbl_map_single(dev, phys, size, iova_mask(iovad), dir,
> + attrs);
> +
> + /*
> + * Untrusted devices should not see padding areas with random leftover
> + * kernel data, so zero the pre- and post-padding.
> + * swiotlb_tbl_map_single() has initialized the bounce buffer proper to
> + * the contents of the original memory buffer.
> + */
> + if (phys != (phys_addr_t)DMA_MAPPING_ERROR && dev_is_untrusted(dev)) {
> + size_t start, virt = (size_t)phys_to_virt(phys);
> +
> + /* Pre-padding */
> + start = iova_align_down(iovad, virt);
> + memset((void *)start, 0, virt - start);
> +
> + /* Post-padding */
> + start = virt + size;
> + memset((void *)start, 0, iova_align(iovad, start) - start);
> + }
> +
> + return phys;
> +}
> +
> dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> unsigned long offset, size_t size, enum dma_data_direction dir,
> unsigned long attrs)
> @@ -1151,42 +1188,14 @@ dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> dma_addr_t iova, dma_mask = dma_get_mask(dev);
>
> /*
> - * If both the physical buffer start address and size are
> - * page aligned, we don't need to use a bounce page.
> + * If both the physical buffer start address and size are page aligned,
> + * we don't need to use a bounce page.
> */
> if (dev_use_swiotlb(dev, size, dir) &&
> iova_offset(iovad, phys | size)) {
> - if (!is_swiotlb_active(dev)) {
... Is it better to move this check into the helper? Simply no-op if a
bounce page is not needed:
if (!dev_use_swiotlb(dev, size, dir) ||
!iova_offset(iovad, phys | size))
return phys;
Thanks,
baolu
On Tue, Apr 29, 2025 at 12:58:18PM +0800, Baolu Lu wrote:
> On 4/28/25 17:22, Leon Romanovsky wrote:
> > From: Christoph Hellwig<hch@lst.de>
> >
> > Split the iommu logic from iommu_dma_map_page into a separate helper.
> > This not only keeps the code neatly separated, but will also allow for
> > reuse in another caller.
> >
> > Signed-off-by: Christoph Hellwig<hch@lst.de>
> > Tested-by: Jens Axboe<axboe@kernel.dk>
> > Reviewed-by: Luis Chamberlain<mcgrof@kernel.org>
> > Signed-off-by: Leon Romanovsky<leonro@nvidia.com>
>
> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
>
> with a nit below ...
>
> > ---
> > drivers/iommu/dma-iommu.c | 73 ++++++++++++++++++++++-----------------
> > 1 file changed, 41 insertions(+), 32 deletions(-)
> >
> > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> > index d3211a8d755e..d7684024c439 100644
> > --- a/drivers/iommu/dma-iommu.c
> > +++ b/drivers/iommu/dma-iommu.c
> > @@ -1138,6 +1138,43 @@ void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
> > arch_sync_dma_for_device(sg_phys(sg), sg->length, dir);
> > }
> > +static phys_addr_t iommu_dma_map_swiotlb(struct device *dev, phys_addr_t phys,
> > + size_t size, enum dma_data_direction dir, unsigned long attrs)
> > +{
> > + struct iommu_domain *domain = iommu_get_dma_domain(dev);
> > + struct iova_domain *iovad = &domain->iova_cookie->iovad;
> > +
> > + if (!is_swiotlb_active(dev)) {
> > + dev_warn_once(dev, "DMA bounce buffers are inactive, unable to map unaligned transaction.\n");
> > + return (phys_addr_t)DMA_MAPPING_ERROR;
> > + }
> > +
> > + trace_swiotlb_bounced(dev, phys, size);
> > +
> > + phys = swiotlb_tbl_map_single(dev, phys, size, iova_mask(iovad), dir,
> > + attrs);
> > +
> > + /*
> > + * Untrusted devices should not see padding areas with random leftover
> > + * kernel data, so zero the pre- and post-padding.
> > + * swiotlb_tbl_map_single() has initialized the bounce buffer proper to
> > + * the contents of the original memory buffer.
> > + */
> > + if (phys != (phys_addr_t)DMA_MAPPING_ERROR && dev_is_untrusted(dev)) {
> > + size_t start, virt = (size_t)phys_to_virt(phys);
> > +
> > + /* Pre-padding */
> > + start = iova_align_down(iovad, virt);
> > + memset((void *)start, 0, virt - start);
> > +
> > + /* Post-padding */
> > + start = virt + size;
> > + memset((void *)start, 0, iova_align(iovad, start) - start);
> > + }
> > +
> > + return phys;
> > +}
> > +
> > dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> > unsigned long offset, size_t size, enum dma_data_direction dir,
> > unsigned long attrs)
> > @@ -1151,42 +1188,14 @@ dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> > dma_addr_t iova, dma_mask = dma_get_mask(dev);
> > /*
> > - * If both the physical buffer start address and size are
> > - * page aligned, we don't need to use a bounce page.
> > + * If both the physical buffer start address and size are page aligned,
> > + * we don't need to use a bounce page.
> > */
> > if (dev_use_swiotlb(dev, size, dir) &&
> > iova_offset(iovad, phys | size)) {
> > - if (!is_swiotlb_active(dev)) {
>
> ... Is it better to move this check into the helper? Simply no-op if a
> bounce page is not needed:
>
> if (!dev_use_swiotlb(dev, size, dir) ||
> !iova_offset(iovad, phys | size))
> return phys;
Am I missing something? iommu_dma_map_page() has more code after this
check, so it is not correct to return immediately:
1189 dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
1190 unsigned long offset, size_t size, enum dma_data_direction dir,
1191 unsigned long attrs)
1192 {
<...>
1201 /*
1202 * If both the physical buffer start address and size are page aligned,
1203 * we don't need to use a bounce page.
1204 */
1205 if (dev_use_swiotlb(dev, size, dir) &&
1206 iova_unaligned(iovad, phys, size)) {
1207 phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);
1208 if (phys == (phys_addr_t)DMA_MAPPING_ERROR)
1209 return DMA_MAPPING_ERROR;
1210 }
1211
1212 if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
1213 arch_sync_dma_for_device(phys, size, dir);
1214
1215 iova = __iommu_dma_map(dev, phys, size, prot, dma_mask);
1216 if (iova == DMA_MAPPING_ERROR)
1217 swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
1218 return iova;
1219 }
>
> Thanks,
> baolu
>
On 4/29/25 13:53, Leon Romanovsky wrote:
> On Tue, Apr 29, 2025 at 12:58:18PM +0800, Baolu Lu wrote:
>> On 4/28/25 17:22, Leon Romanovsky wrote:
>>> From: Christoph Hellwig<hch@lst.de>
>>>
>>> Split the iommu logic from iommu_dma_map_page into a separate helper.
>>> This not only keeps the code neatly separated, but will also allow for
>>> reuse in another caller.
>>>
>>> Signed-off-by: Christoph Hellwig<hch@lst.de>
>>> Tested-by: Jens Axboe<axboe@kernel.dk>
>>> Reviewed-by: Luis Chamberlain<mcgrof@kernel.org>
>>> Signed-off-by: Leon Romanovsky<leonro@nvidia.com>
>>
>> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
>>
>> with a nit below ...
>>
>>> ---
>>> drivers/iommu/dma-iommu.c | 73 ++++++++++++++++++++++-----------------
>>> 1 file changed, 41 insertions(+), 32 deletions(-)
>>>
>>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>>> index d3211a8d755e..d7684024c439 100644
>>> --- a/drivers/iommu/dma-iommu.c
>>> +++ b/drivers/iommu/dma-iommu.c
>>> @@ -1138,6 +1138,43 @@ void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
>>> arch_sync_dma_for_device(sg_phys(sg), sg->length, dir);
>>> }
>>> +static phys_addr_t iommu_dma_map_swiotlb(struct device *dev, phys_addr_t phys,
>>> + size_t size, enum dma_data_direction dir, unsigned long attrs)
>>> +{
>>> + struct iommu_domain *domain = iommu_get_dma_domain(dev);
>>> + struct iova_domain *iovad = &domain->iova_cookie->iovad;
>>> +
>>> + if (!is_swiotlb_active(dev)) {
>>> + dev_warn_once(dev, "DMA bounce buffers are inactive, unable to map unaligned transaction.\n");
>>> + return (phys_addr_t)DMA_MAPPING_ERROR;
>>> + }
>>> +
>>> + trace_swiotlb_bounced(dev, phys, size);
>>> +
>>> + phys = swiotlb_tbl_map_single(dev, phys, size, iova_mask(iovad), dir,
>>> + attrs);
>>> +
>>> + /*
>>> + * Untrusted devices should not see padding areas with random leftover
>>> + * kernel data, so zero the pre- and post-padding.
>>> + * swiotlb_tbl_map_single() has initialized the bounce buffer proper to
>>> + * the contents of the original memory buffer.
>>> + */
>>> + if (phys != (phys_addr_t)DMA_MAPPING_ERROR && dev_is_untrusted(dev)) {
>>> + size_t start, virt = (size_t)phys_to_virt(phys);
>>> +
>>> + /* Pre-padding */
>>> + start = iova_align_down(iovad, virt);
>>> + memset((void *)start, 0, virt - start);
>>> +
>>> + /* Post-padding */
>>> + start = virt + size;
>>> + memset((void *)start, 0, iova_align(iovad, start) - start);
>>> + }
>>> +
>>> + return phys;
>>> +}
>>> +
>>> dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
>>> unsigned long offset, size_t size, enum dma_data_direction dir,
>>> unsigned long attrs)
>>> @@ -1151,42 +1188,14 @@ dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
>>> dma_addr_t iova, dma_mask = dma_get_mask(dev);
>>> /*
>>> - * If both the physical buffer start address and size are
>>> - * page aligned, we don't need to use a bounce page.
>>> + * If both the physical buffer start address and size are page aligned,
>>> + * we don't need to use a bounce page.
>>> */
>>> if (dev_use_swiotlb(dev, size, dir) &&
>>> iova_offset(iovad, phys | size)) {
>>> - if (!is_swiotlb_active(dev)) {
>>
>> ... Is it better to move this check into the helper? Simply no-op if a
>> bounce page is not needed:
>>
>> if (!dev_use_swiotlb(dev, size, dir) ||
>> !iova_offset(iovad, phys | size))
>> return phys;
>
> Am I missing something? iommu_dma_map_page() has more code after this
> check, so it is not correct to return immediately:
>
> 1189 dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> 1190 unsigned long offset, size_t size, enum dma_data_direction dir,
> 1191 unsigned long attrs)
> 1192 {
>
> <...>
>
> 1201 /*
> 1202 * If both the physical buffer start address and size are page aligned,
> 1203 * we don't need to use a bounce page.
> 1204 */
> 1205 if (dev_use_swiotlb(dev, size, dir) &&
> 1206 iova_unaligned(iovad, phys, size)) {
> 1207 phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);
> 1208 if (phys == (phys_addr_t)DMA_MAPPING_ERROR)
> 1209 return DMA_MAPPING_ERROR;
> 1210 }
> 1211
> 1212 if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> 1213 arch_sync_dma_for_device(phys, size, dir);
> 1214
> 1215 iova = __iommu_dma_map(dev, phys, size, prot, dma_mask);
> 1216 if (iova == DMA_MAPPING_ERROR)
> 1217 swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
> 1218 return iova;
> 1219 }
static phys_addr_t iommu_dma_map_swiotlb(struct device *dev, phys_addr_t
phys,
size_t size, enum dma_data_direction dir, unsigned long attrs)
{
<...>
/*
* If both the physical buffer start address and size are page aligned,
* we don't need to use a bounce page.
*/
if (!dev_use_swiotlb(dev, size, dir) ||
!iova_offset(iovad, phys | size))
return phys;
<...>
}
Then,
dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
unsigned long offset, size_t size, enum dma_data_direction dir,
unsigned long attrs)
{
<...>
phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);
if (phys == (phys_addr_t)DMA_MAPPING_ERROR)
return DMA_MAPPING_ERROR;
<...>
}
Thanks,
baolu
On Tue, Apr 29, 2025 at 01:58:06PM +0800, Baolu Lu wrote:
> On 4/29/25 13:53, Leon Romanovsky wrote:
> > On Tue, Apr 29, 2025 at 12:58:18PM +0800, Baolu Lu wrote:
> > > On 4/28/25 17:22, Leon Romanovsky wrote:
> > > > From: Christoph Hellwig<hch@lst.de>
> > > >
> > > > Split the iommu logic from iommu_dma_map_page into a separate helper.
> > > > This not only keeps the code neatly separated, but will also allow for
> > > > reuse in another caller.
> > > >
> > > > Signed-off-by: Christoph Hellwig<hch@lst.de>
> > > > Tested-by: Jens Axboe<axboe@kernel.dk>
> > > > Reviewed-by: Luis Chamberlain<mcgrof@kernel.org>
> > > > Signed-off-by: Leon Romanovsky<leonro@nvidia.com>
> > >
> > > Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
> > >
> > > with a nit below ...
> > >
> > > > ---
> > > > drivers/iommu/dma-iommu.c | 73 ++++++++++++++++++++++-----------------
> > > > 1 file changed, 41 insertions(+), 32 deletions(-)
> > > >
> > > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> > > > index d3211a8d755e..d7684024c439 100644
> > > > --- a/drivers/iommu/dma-iommu.c
> > > > +++ b/drivers/iommu/dma-iommu.c
> > > > @@ -1138,6 +1138,43 @@ void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
> > > > arch_sync_dma_for_device(sg_phys(sg), sg->length, dir);
> > > > }
> > > > +static phys_addr_t iommu_dma_map_swiotlb(struct device *dev, phys_addr_t phys,
> > > > + size_t size, enum dma_data_direction dir, unsigned long attrs)
> > > > +{
> > > > + struct iommu_domain *domain = iommu_get_dma_domain(dev);
> > > > + struct iova_domain *iovad = &domain->iova_cookie->iovad;
> > > > +
> > > > + if (!is_swiotlb_active(dev)) {
> > > > + dev_warn_once(dev, "DMA bounce buffers are inactive, unable to map unaligned transaction.\n");
> > > > + return (phys_addr_t)DMA_MAPPING_ERROR;
> > > > + }
> > > > +
> > > > + trace_swiotlb_bounced(dev, phys, size);
> > > > +
> > > > + phys = swiotlb_tbl_map_single(dev, phys, size, iova_mask(iovad), dir,
> > > > + attrs);
> > > > +
> > > > + /*
> > > > + * Untrusted devices should not see padding areas with random leftover
> > > > + * kernel data, so zero the pre- and post-padding.
> > > > + * swiotlb_tbl_map_single() has initialized the bounce buffer proper to
> > > > + * the contents of the original memory buffer.
> > > > + */
> > > > + if (phys != (phys_addr_t)DMA_MAPPING_ERROR && dev_is_untrusted(dev)) {
> > > > + size_t start, virt = (size_t)phys_to_virt(phys);
> > > > +
> > > > + /* Pre-padding */
> > > > + start = iova_align_down(iovad, virt);
> > > > + memset((void *)start, 0, virt - start);
> > > > +
> > > > + /* Post-padding */
> > > > + start = virt + size;
> > > > + memset((void *)start, 0, iova_align(iovad, start) - start);
> > > > + }
> > > > +
> > > > + return phys;
> > > > +}
> > > > +
> > > > dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> > > > unsigned long offset, size_t size, enum dma_data_direction dir,
> > > > unsigned long attrs)
> > > > @@ -1151,42 +1188,14 @@ dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> > > > dma_addr_t iova, dma_mask = dma_get_mask(dev);
> > > > /*
> > > > - * If both the physical buffer start address and size are
> > > > - * page aligned, we don't need to use a bounce page.
> > > > + * If both the physical buffer start address and size are page aligned,
> > > > + * we don't need to use a bounce page.
> > > > */
> > > > if (dev_use_swiotlb(dev, size, dir) &&
> > > > iova_offset(iovad, phys | size)) {
> > > > - if (!is_swiotlb_active(dev)) {
> > >
> > > ... Is it better to move this check into the helper? Simply no-op if a
> > > bounce page is not needed:
> > >
> > > if (!dev_use_swiotlb(dev, size, dir) ||
> > > !iova_offset(iovad, phys | size))
> > > return phys;
> >
> > Am I missing something? iommu_dma_map_page() has more code after this
> > check, so it is not correct to return immediately:
> >
> > 1189 dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> > 1190 unsigned long offset, size_t size, enum dma_data_direction dir,
> > 1191 unsigned long attrs)
> > 1192 {
> >
> > <...>
> >
> > 1201 /*
> > 1202 * If both the physical buffer start address and size are page aligned,
> > 1203 * we don't need to use a bounce page.
> > 1204 */
> > 1205 if (dev_use_swiotlb(dev, size, dir) &&
> > 1206 iova_unaligned(iovad, phys, size)) {
> > 1207 phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);
> > 1208 if (phys == (phys_addr_t)DMA_MAPPING_ERROR)
> > 1209 return DMA_MAPPING_ERROR;
> > 1210 }
> > 1211
> > 1212 if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> > 1213 arch_sync_dma_for_device(phys, size, dir);
> > 1214
> > 1215 iova = __iommu_dma_map(dev, phys, size, prot, dma_mask);
> > 1216 if (iova == DMA_MAPPING_ERROR)
> > 1217 swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
> > 1218 return iova;
> > 1219 }
>
> static phys_addr_t iommu_dma_map_swiotlb(struct device *dev, phys_addr_t
> phys,
> size_t size, enum dma_data_direction dir, unsigned long attrs)
> {
> <...>
> /*
> * If both the physical buffer start address and size are page aligned,
> * we don't need to use a bounce page.
> */
> if (!dev_use_swiotlb(dev, size, dir) ||
> !iova_offset(iovad, phys | size))
> return phys;
> <...>
> }
>
> Then,
>
> dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> unsigned long offset, size_t size, enum dma_data_direction dir,
> unsigned long attrs)
> {
> <...>
> phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);
> if (phys == (phys_addr_t)DMA_MAPPING_ERROR)
> return DMA_MAPPING_ERROR;
> <...>
> }
Such change will cause to extra function call for everyone who doesn't
use SWIOTLB (RDMA, HMM e.t.c).
In addition, iommu_dma_map_swiotlb() is called through
dma_iova_link ->
iommu_dma_iova_link_swiotlb ->
iommu_dma_iova_bounce_and_link() ->
iommu_dma_map_swiotlb()
and dma_iova_link() has this "if (dev_use_swiotlb(dev, size, dir) && iova_unaligned(iovad, phys, size))"
very early at call stack.
So, in dma_iova_link() we will find ourselves with same check twice.
Thanks
>
> Thanks,
> baolu
>
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