[PATCH 1/1] nvme: Fix PRP list calculation for non-4k system page size

[PATCH 1/1] nvme: Fix PRP list calculation for non-4k system page size

[Brian King]

From: Murali Iyer <mniyer@us.ibm.com>

PRP list calculation is supposed to be based on device's page size.
Systems with page size larger than device's page size cause corruption
to the name space as well as system memory with out this fix.
Systems like x86 might not experience this issue because it uses
PAGE_SIZE of 4K where as powerpc uses PAGE_SIZE of 64k while NVMe device's
page size varies depending upon the vendor.

Signed-off-by: Murali Iyer <mniyer at us.ibm.com>
Signed-off-by: Brian King <brking at linux.vnet.ibm.com>
---

 drivers/block/nvme-core.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN drivers/block/nvme-core.c~nvme_power drivers/block/nvme-core.c
--- linux-nvme/drivers/block/nvme-core.c~nvme_power	2015-03-24 17:12:09.912743224 -0500
+++ linux-nvme-bjking1/drivers/block/nvme-core.c	2015-03-24 17:16:13.414970447 -0500
@@ -503,12 +503,12 @@ int nvme_setup_prps(struct nvme_dev *dev
 	struct scatterlist *sg = iod->sg;
 	int dma_len = sg_dma_len(sg);
 	u64 dma_addr = sg_dma_address(sg);
-	int offset = offset_in_page(dma_addr);
+	u32 page_size = dev->page_size;
+	int offset = dma_addr % page_size;
 	__le64 *prp_list;
 	__le64 **list = iod_list(iod);
 	dma_addr_t prp_dma;
 	int nprps, i;
-	u32 page_size = dev->page_size;
 
 	length -= (page_size - offset);
 	if (length <= 0)
_

[PATCH 1/1] nvme: Fix PRP list calculation for non-4k system page size

[Keith Busch]

On Tue, 24 Mar 2015, Brian King wrote:
> PRP list calculation is supposed to be based on device's page size.
> Systems with page size larger than device's page size cause corruption
> to the name space as well as system memory with out this fix.
> Systems like x86 might not experience this issue because it uses
> PAGE_SIZE of 4K where as powerpc uses PAGE_SIZE of 64k while NVMe device's
> page size varies depending upon the vendor.

Darn, I thought we had this working. I must have just gotten lucky when
testing on an 8k page. Thanks for the fix.

> -	int offset = offset_in_page(dma_addr);
> +	u32 page_size = dev->page_size;
> +	int offset = dma_addr % page_size;

Trying to micro-optimize the io path to have fewer divisions. This should
work out the same if changed to:

 	int offset = dma_addr & (page_size - 1);

The page_size is always a power of two, but I don't think the compiler
knows that.

[PATCH v2 1/1] nvme: Fix PRP list calculation for non-4k system page size

[Brian King]

From: Murali Iyer <mniyer@us.ibm.com>

PRP list calculation is supposed to be based on device's page size.
Systems with page size larger than device's page size cause corruption
to the name space as well as system memory with out this fix.
Systems like x86 might not experience this issue because it uses
PAGE_SIZE of 4K where as powerpc uses PAGE_SIZE of 64k while NVMe device's
page size varies depending upon the vendor.

Signed-off-by: Murali Iyer <mniyer at us.ibm.com>
Signed-off-by: Brian King <brking at linux.vnet.ibm.com>
---

 drivers/block/nvme-core.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN drivers/block/nvme-core.c~nvme_power drivers/block/nvme-core.c
--- linux-nvme/drivers/block/nvme-core.c~nvme_power	2015-03-24 17:12:09.912743224 -0500
+++ linux-nvme-bjking1/drivers/block/nvme-core.c	2015-03-25 09:25:43.580260410 -0500
@@ -503,12 +503,12 @@ int nvme_setup_prps(struct nvme_dev *dev
 	struct scatterlist *sg = iod->sg;
 	int dma_len = sg_dma_len(sg);
 	u64 dma_addr = sg_dma_address(sg);
-	int offset = offset_in_page(dma_addr);
+	u32 page_size = dev->page_size;
+	int offset = dma_addr & (page_size - 1);
 	__le64 *prp_list;
 	__le64 **list = iod_list(iod);
 	dma_addr_t prp_dma;
 	int nprps, i;
-	u32 page_size = dev->page_size;
 
 	length -= (page_size - offset);
 	if (length <= 0)
_

[PATCH v2 1/1] nvme: Fix PRP list calculation for non-4k system page size

[Keith Busch]

On Thu, 26 Mar 2015, Brian King wrote:
> From: Murali Iyer <mniyer at us.ibm.com>
>
> PRP list calculation is supposed to be based on device's page size.
> Systems with page size larger than device's page size cause corruption
> to the name space as well as system memory with out this fix.
> Systems like x86 might not experience this issue because it uses
> PAGE_SIZE of 4K where as powerpc uses PAGE_SIZE of 64k while NVMe device's
> page size varies depending upon the vendor.

Thanks!

Acked-by: Keith Busch <keith.busch at intel.com>

> Signed-off-by: Murali Iyer <mniyer at us.ibm.com>
> Signed-off-by: Brian King <brking at linux.vnet.ibm.com>

[PATCH v2 1/1] nvme: Fix PRP list calculation for non-4k system page size

[Jens Axboe]

On 03/26/2015 10:19 AM, Keith Busch wrote:
> On Thu, 26 Mar 2015, Brian King wrote:
>> From: Murali Iyer <mniyer at us.ibm.com>
>>
>> PRP list calculation is supposed to be based on device's page size.
>> Systems with page size larger than device's page size cause corruption
>> to the name space as well as system memory with out this fix.
>> Systems like x86 might not experience this issue because it uses
>> PAGE_SIZE of 4K where as powerpc uses PAGE_SIZE of 64k while NVMe
>> device's
>> page size varies depending upon the vendor.
>
> Thanks!
>
> Acked-by: Keith Busch <keith.busch at intel.com>

Added for 4.1.

-- 
Jens Axboe