Re: [RFC PATCH 03/15] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()
On 2020-11-10 4:25 p.m., Bjorn Helgaas wrote:
> On Fri, Nov 06, 2020 at 10:00:24AM -0700, Logan Gunthorpe wrote:
>> Introduce pci_p2pdma_should_map_bus() which is meant to be called by
>> dma map functions to determine how to map a given p2pdma page.
>
> s/dma/DMA/ for consistency (also below in function comment)
>
>> pci_p2pdma_bus_offset() is also added to allow callers to get the bus
>> offset if they need to map the bus address.
>>
>> Signed-off-by: Logan Gunthorpe
>> ---
>> drivers/pci/p2pdma.c | 46 ++
>> include/linux/pci-p2pdma.h | 11 +
>> 2 files changed, 57 insertions(+)
>>
>> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
>> index ea8472278b11..9961e779f430 100644
>> --- a/drivers/pci/p2pdma.c
>> +++ b/drivers/pci/p2pdma.c
>> @@ -930,6 +930,52 @@ void pci_p2pdma_unmap_sg_attrs(struct device *dev,
>> struct scatterlist *sg,
>> }
>> EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs);
>>
>> +/**
>> + * pci_p2pdma_bus_offset - returns the bus offset for a given page
>> + * @page: page to get the offset for
>> + *
>> + * Must be passed a pci p2pdma page.
>
> s/pci/PCI/
>
>> + */
>> +u64 pci_p2pdma_bus_offset(struct page *page)
>> +{
>> +struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(page->pgmap);
>> +
>> +WARN_ON(!is_pci_p2pdma_page(page));
>> +
>> +return p2p_pgmap->bus_offset;
>> +}
>> +EXPORT_SYMBOL_GPL(pci_p2pdma_bus_offset);
>> +
>> +/**
>> + * pci_p2pdma_should_map_bus - determine if a dma mapping should use the
>> + * bus address
>> + * @dev: device doing the DMA request
>> + * @pgmap: dev_pagemap structure for the mapping
>> + *
>> + * Returns 1 if the page should be mapped with a bus address, 0 otherwise
>> + * and -1 the device should not be mapping P2PDMA pages.
>
> I think this is missing a word.
>
> I'm not really sure how to interpret the "should" in
> pci_p2pdma_should_map_bus(). If this returns -1, does that mean the
> patches *cannot* be mapped? They *could* be mapped, but you really
> *shouldn't*? Something else?
>
> 1 means page should be mapped with bus address. 0 means ... what,
> exactly? It should be mapped with some different address?
1 means it must be mapped with a bus address
0 means it may be mapped normally (through the IOMMU or just with a
direct physical address)
-1 means it cannot be mapped and should fail (ie. if it must go through
the IOMMU, but the IOMMU is not in the whitelist).
> Sorry these are naive questions because I don't know how all this
> works.
Thanks for the review. Definitely points out some questionable language
that I used. I'll reword this if/when it goes further.
Logan
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Re: [RFC PATCH 03/15] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()
On Fri, Nov 06, 2020 at 10:00:24AM -0700, Logan Gunthorpe wrote:
> Introduce pci_p2pdma_should_map_bus() which is meant to be called by
> dma map functions to determine how to map a given p2pdma page.
s/dma/DMA/ for consistency (also below in function comment)
> pci_p2pdma_bus_offset() is also added to allow callers to get the bus
> offset if they need to map the bus address.
>
> Signed-off-by: Logan Gunthorpe
> ---
> drivers/pci/p2pdma.c | 46 ++
> include/linux/pci-p2pdma.h | 11 +
> 2 files changed, 57 insertions(+)
>
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index ea8472278b11..9961e779f430 100644
> --- a/drivers/pci/p2pdma.c
> +++ b/drivers/pci/p2pdma.c
> @@ -930,6 +930,52 @@ void pci_p2pdma_unmap_sg_attrs(struct device *dev,
> struct scatterlist *sg,
> }
> EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs);
>
> +/**
> + * pci_p2pdma_bus_offset - returns the bus offset for a given page
> + * @page: page to get the offset for
> + *
> + * Must be passed a pci p2pdma page.
s/pci/PCI/
> + */
> +u64 pci_p2pdma_bus_offset(struct page *page)
> +{
> + struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(page->pgmap);
> +
> + WARN_ON(!is_pci_p2pdma_page(page));
> +
> + return p2p_pgmap->bus_offset;
> +}
> +EXPORT_SYMBOL_GPL(pci_p2pdma_bus_offset);
> +
> +/**
> + * pci_p2pdma_should_map_bus - determine if a dma mapping should use the
> + * bus address
> + * @dev: device doing the DMA request
> + * @pgmap: dev_pagemap structure for the mapping
> + *
> + * Returns 1 if the page should be mapped with a bus address, 0 otherwise
> + * and -1 the device should not be mapping P2PDMA pages.
I think this is missing a word.
I'm not really sure how to interpret the "should" in
pci_p2pdma_should_map_bus(). If this returns -1, does that mean the
patches *cannot* be mapped? They *could* be mapped, but you really
*shouldn't*? Something else?
1 means page should be mapped with bus address. 0 means ... what,
exactly? It should be mapped with some different address?
Sorry these are naive questions because I don't know how all this
works.
> + */
> +int pci_p2pdma_should_map_bus(struct device *dev, struct dev_pagemap *pgmap)
> +{
> + struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(pgmap);
> + struct pci_dev *client;
> +
> + if (!dev_is_pci(dev))
> + return -1;
> +
> + client = to_pci_dev(dev);
> +
> + switch (pci_p2pdma_map_type(p2p_pgmap->provider, client)) {
> + case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
> + return 0;
> + case PCI_P2PDMA_MAP_BUS_ADDR:
> + return 1;
> + default:
> + return -1;
> + }
> +}
> +EXPORT_SYMBOL_GPL(pci_p2pdma_should_map_bus);
> +
> /**
> * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store
> * to enable p2pdma
> diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
> index 8318a97c9c61..fc5de47eeac4 100644
> --- a/include/linux/pci-p2pdma.h
> +++ b/include/linux/pci-p2pdma.h
> @@ -34,6 +34,8 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct
> scatterlist *sg,
> int nents, enum dma_data_direction dir, unsigned long attrs);
> void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
> int nents, enum dma_data_direction dir, unsigned long attrs);
> +u64 pci_p2pdma_bus_offset(struct page *page);
> +int pci_p2pdma_should_map_bus(struct device *dev, struct dev_pagemap *pgmap);
> int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
> bool *use_p2pdma);
> ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
> @@ -83,6 +85,15 @@ static inline void pci_p2pmem_free_sgl(struct pci_dev
> *pdev,
> static inline void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
> {
> }
> +static inline u64 pci_p2pdma_bus_offset(struct page *page)
> +{
> + return -1;
> +}
> +static inline int pci_p2pdma_should_map_bus(struct device *dev,
> + struct dev_pagemap *pgmap)
> +{
> + return -1;
> +}
> static inline int pci_p2pdma_map_sg_attrs(struct device *dev,
> struct scatterlist *sg, int nents, enum dma_data_direction dir,
> unsigned long attrs)
> --
> 2.20.1
>
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[RFC PATCH 03/15] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()
Introduce pci_p2pdma_should_map_bus() which is meant to be called by
dma map functions to determine how to map a given p2pdma page.
pci_p2pdma_bus_offset() is also added to allow callers to get the bus
offset if they need to map the bus address.
Signed-off-by: Logan Gunthorpe
---
drivers/pci/p2pdma.c | 46 ++
include/linux/pci-p2pdma.h | 11 +
2 files changed, 57 insertions(+)
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index ea8472278b11..9961e779f430 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -930,6 +930,52 @@ void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct
scatterlist *sg,
}
EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs);
+/**
+ * pci_p2pdma_bus_offset - returns the bus offset for a given page
+ * @page: page to get the offset for
+ *
+ * Must be passed a pci p2pdma page.
+ */
+u64 pci_p2pdma_bus_offset(struct page *page)
+{
+ struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(page->pgmap);
+
+ WARN_ON(!is_pci_p2pdma_page(page));
+
+ return p2p_pgmap->bus_offset;
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_bus_offset);
+
+/**
+ * pci_p2pdma_should_map_bus - determine if a dma mapping should use the
+ * bus address
+ * @dev: device doing the DMA request
+ * @pgmap: dev_pagemap structure for the mapping
+ *
+ * Returns 1 if the page should be mapped with a bus address, 0 otherwise
+ * and -1 the device should not be mapping P2PDMA pages.
+ */
+int pci_p2pdma_should_map_bus(struct device *dev, struct dev_pagemap *pgmap)
+{
+ struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(pgmap);
+ struct pci_dev *client;
+
+ if (!dev_is_pci(dev))
+ return -1;
+
+ client = to_pci_dev(dev);
+
+ switch (pci_p2pdma_map_type(p2p_pgmap->provider, client)) {
+ case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
+ return 0;
+ case PCI_P2PDMA_MAP_BUS_ADDR:
+ return 1;
+ default:
+ return -1;
+ }
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_should_map_bus);
+
/**
* pci_p2pdma_enable_store - parse a configfs/sysfs attribute store
* to enable p2pdma
diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
index 8318a97c9c61..fc5de47eeac4 100644
--- a/include/linux/pci-p2pdma.h
+++ b/include/linux/pci-p2pdma.h
@@ -34,6 +34,8 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct
scatterlist *sg,
int nents, enum dma_data_direction dir, unsigned long attrs);
void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction dir, unsigned long attrs);
+u64 pci_p2pdma_bus_offset(struct page *page);
+int pci_p2pdma_should_map_bus(struct device *dev, struct dev_pagemap *pgmap);
int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
bool *use_p2pdma);
ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
@@ -83,6 +85,15 @@ static inline void pci_p2pmem_free_sgl(struct pci_dev *pdev,
static inline void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
{
}
+static inline u64 pci_p2pdma_bus_offset(struct page *page)
+{
+ return -1;
+}
+static inline int pci_p2pdma_should_map_bus(struct device *dev,
+ struct dev_pagemap *pgmap)
+{
+ return -1;
+}
static inline int pci_p2pdma_map_sg_attrs(struct device *dev,
struct scatterlist *sg, int nents, enum dma_data_direction dir,
unsigned long attrs)
--
2.20.1
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