diff mbox series

[12/16] nvme-pci: Check DMA ops when indicating support for PCI P2PDMA

Message ID 20210408170123.8788-13-logang@deltatee.com (mailing list archive)
State New
Headers show
Series Add new DMA mapping operation for P2PDMA | expand

Commit Message

Logan Gunthorpe April 8, 2021, 5:01 p.m. UTC
Introduce a supports_pci_p2pdma() operation in nvme_ctrl_ops to
replace the fixed NVME_F_PCI_P2PDMA flag such that the dma_map_ops
flags can be checked for PCI P2PDMA support.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 drivers/nvme/host/core.c |  3 ++-
 drivers/nvme/host/nvme.h |  2 +-
 drivers/nvme/host/pci.c  | 11 +++++++++--
 3 files changed, 12 insertions(+), 4 deletions(-)

Comments

John Hubbard May 3, 2021, 1:29 a.m. UTC | #1
On 4/8/21 10:01 AM, Logan Gunthorpe wrote:
> Introduce a supports_pci_p2pdma() operation in nvme_ctrl_ops to
> replace the fixed NVME_F_PCI_P2PDMA flag such that the dma_map_ops
> flags can be checked for PCI P2PDMA support.
> 
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> ---
>   drivers/nvme/host/core.c |  3 ++-
>   drivers/nvme/host/nvme.h |  2 +-
>   drivers/nvme/host/pci.c  | 11 +++++++++--
>   3 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 0896e21642be..223419454516 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -3907,7 +3907,8 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
>   		blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, ns->queue);
>   
>   	blk_queue_flag_set(QUEUE_FLAG_NONROT, ns->queue);
> -	if (ctrl->ops->flags & NVME_F_PCI_P2PDMA)
> +	if (ctrl->ops->supports_pci_p2pdma &&
> +	    ctrl->ops->supports_pci_p2pdma(ctrl))

This is a little excessive, as I suspected. How about providing a
default .supports_pci_p2pdma routine that returns false, so that
the op is always available (non-null)? By "default", maybe that
means either requiring an init_the_ops_struct() routine to be
used, and/or checking all the users of struct nvme_ctrl_ops.

Another idea: maybe you don't really need a bool .supports_pci_p2pdma()
routine at all, because the existing .flags really is about right.
You just need the flags to be filled in dynamically. So, do that
during nvme_pci setup/init time: that's when this module would call
dma_pci_p2pdma_supported().

Actually, I think that second idea simplifies things quite a
bit, but only if it's possible. I haven't worked through the
startup order of calls in nvme_pci.

thanks,
Logan Gunthorpe May 3, 2021, 5:17 p.m. UTC | #2
On 2021-05-02 7:29 p.m., John Hubbard wrote:
> On 4/8/21 10:01 AM, Logan Gunthorpe wrote:
>> Introduce a supports_pci_p2pdma() operation in nvme_ctrl_ops to
>> replace the fixed NVME_F_PCI_P2PDMA flag such that the dma_map_ops
>> flags can be checked for PCI P2PDMA support.
>>
>> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
>> ---
>>   drivers/nvme/host/core.c |  3 ++-
>>   drivers/nvme/host/nvme.h |  2 +-
>>   drivers/nvme/host/pci.c  | 11 +++++++++--
>>   3 files changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>> index 0896e21642be..223419454516 100644
>> --- a/drivers/nvme/host/core.c
>> +++ b/drivers/nvme/host/core.c
>> @@ -3907,7 +3907,8 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
>>   		blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, ns->queue);
>>   
>>   	blk_queue_flag_set(QUEUE_FLAG_NONROT, ns->queue);
>> -	if (ctrl->ops->flags & NVME_F_PCI_P2PDMA)
>> +	if (ctrl->ops->supports_pci_p2pdma &&
>> +	    ctrl->ops->supports_pci_p2pdma(ctrl))
> 
> This is a little excessive, as I suspected. How about providing a
> default .supports_pci_p2pdma routine that returns false, so that
> the op is always available (non-null)? By "default", maybe that
> means either requiring an init_the_ops_struct() routine to be
> used, and/or checking all the users of struct nvme_ctrl_ops.

Honestly that sounds much more messy to me than simply checking if it's
NULL before using it (which is a common, accepted pattern for ops).

> Another idea: maybe you don't really need a bool .supports_pci_p2pdma()
> routine at all, because the existing .flags really is about right.
> You just need the flags to be filled in dynamically. So, do that
> during nvme_pci setup/init time: that's when this module would call
> dma_pci_p2pdma_supported().

If the flag is filled in dynamically, then the ops struct would have to
be non-constant. Ops structs should be constant for security reasons.

Logan
John Hubbard May 4, 2021, 12:17 a.m. UTC | #3
On 5/3/21 10:17 AM, Logan Gunthorpe wrote:
...
>>>    	blk_queue_flag_set(QUEUE_FLAG_NONROT, ns->queue);
>>> -	if (ctrl->ops->flags & NVME_F_PCI_P2PDMA)
>>> +	if (ctrl->ops->supports_pci_p2pdma &&
>>> +	    ctrl->ops->supports_pci_p2pdma(ctrl))
>>
>> This is a little excessive, as I suspected. How about providing a
>> default .supports_pci_p2pdma routine that returns false, so that
>> the op is always available (non-null)? By "default", maybe that
>> means either requiring an init_the_ops_struct() routine to be
>> used, and/or checking all the users of struct nvme_ctrl_ops.
> 
> Honestly that sounds much more messy to me than simply checking if it's
> NULL before using it (which is a common, accepted pattern for ops).

OK, it's a minor suggestion, so feel free to ignore if you prefer it
the other way, sure.

> 
>> Another idea: maybe you don't really need a bool .supports_pci_p2pdma()
>> routine at all, because the existing .flags really is about right.
>> You just need the flags to be filled in dynamically. So, do that
>> during nvme_pci setup/init time: that's when this module would call
>> dma_pci_p2pdma_supported().
> 
> If the flag is filled in dynamically, then the ops struct would have to
> be non-constant. Ops structs should be constant for security reasons.
> 

Hadn't thought about keeping ops structs constant. OK.

thanks,
diff mbox series

Patch

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 0896e21642be..223419454516 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3907,7 +3907,8 @@  static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
 		blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, ns->queue);
 
 	blk_queue_flag_set(QUEUE_FLAG_NONROT, ns->queue);
-	if (ctrl->ops->flags & NVME_F_PCI_P2PDMA)
+	if (ctrl->ops->supports_pci_p2pdma &&
+	    ctrl->ops->supports_pci_p2pdma(ctrl))
 		blk_queue_flag_set(QUEUE_FLAG_PCI_P2PDMA, ns->queue);
 
 	ns->queue->queuedata = ns;
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 07b34175c6ce..9c04df982d2c 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -473,7 +473,6 @@  struct nvme_ctrl_ops {
 	unsigned int flags;
 #define NVME_F_FABRICS			(1 << 0)
 #define NVME_F_METADATA_SUPPORTED	(1 << 1)
-#define NVME_F_PCI_P2PDMA		(1 << 2)
 	int (*reg_read32)(struct nvme_ctrl *ctrl, u32 off, u32 *val);
 	int (*reg_write32)(struct nvme_ctrl *ctrl, u32 off, u32 val);
 	int (*reg_read64)(struct nvme_ctrl *ctrl, u32 off, u64 *val);
@@ -481,6 +480,7 @@  struct nvme_ctrl_ops {
 	void (*submit_async_event)(struct nvme_ctrl *ctrl);
 	void (*delete_ctrl)(struct nvme_ctrl *ctrl);
 	int (*get_address)(struct nvme_ctrl *ctrl, char *buf, int size);
+	bool (*supports_pci_p2pdma)(struct nvme_ctrl *ctrl);
 };
 
 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 7249ae74f71f..14f092973792 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2759,17 +2759,24 @@  static int nvme_pci_get_address(struct nvme_ctrl *ctrl, char *buf, int size)
 	return snprintf(buf, size, "%s\n", dev_name(&pdev->dev));
 }
 
+static bool nvme_pci_supports_pci_p2pdma(struct nvme_ctrl *ctrl)
+{
+	struct nvme_dev *dev = to_nvme_dev(ctrl);
+
+	return dma_pci_p2pdma_supported(dev->dev);
+}
+
 static const struct nvme_ctrl_ops nvme_pci_ctrl_ops = {
 	.name			= "pcie",
 	.module			= THIS_MODULE,
-	.flags			= NVME_F_METADATA_SUPPORTED |
-				  NVME_F_PCI_P2PDMA,
+	.flags			= NVME_F_METADATA_SUPPORTED,
 	.reg_read32		= nvme_pci_reg_read32,
 	.reg_write32		= nvme_pci_reg_write32,
 	.reg_read64		= nvme_pci_reg_read64,
 	.free_ctrl		= nvme_pci_free_ctrl,
 	.submit_async_event	= nvme_pci_submit_async_event,
 	.get_address		= nvme_pci_get_address,
+	.supports_pci_p2pdma	= nvme_pci_supports_pci_p2pdma,
 };
 
 static int nvme_dev_map(struct nvme_dev *dev)