[PATCH net] gve: fix dma sync bug where not all pages synced

[PATCH net] gve: fix dma sync bug where not all pages synced

[Adi Suresh]

The previous commit "Fixes DMA synchronization" had a bug where the
last page in the memory range could not be synced. This change fixes
the behavior so that all the required pages are synced.

Signed-off-by: Adi Suresh <adisuresh@google.com>
Reviewed-by: Catherine Sullivan <csully@google.com>
---
 drivers/net/ethernet/google/gve/gve_tx.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/google/gve/gve_tx.c b/drivers/net/ethernet/google/gve/gve_tx.c
index 0a9a7ee2a866..89271380bbfd 100644
--- a/drivers/net/ethernet/google/gve/gve_tx.c
+++ b/drivers/net/ethernet/google/gve/gve_tx.c
@@ -393,12 +393,12 @@ static void gve_tx_fill_seg_desc(union gve_tx_desc *seg_desc,
 static void gve_dma_sync_for_device(struct device *dev, dma_addr_t *page_buses,
 				    u64 iov_offset, u64 iov_len)
 {
-	dma_addr_t dma;
-	u64 addr;
+	u64 last_page = (iov_offset + iov_len - 1) / PAGE_SIZE;
+	u64 first_page = iov_offset / PAGE_SIZE;
+	u64 page;
 
-	for (addr = iov_offset; addr < iov_offset + iov_len;
-	     addr += PAGE_SIZE) {
-		dma = page_buses[addr / PAGE_SIZE];
+	for (page = first_page; page <= last_page; page++) {
+		dma_addr_t dma = page_buses[page];
 		dma_sync_single_for_device(dev, dma, PAGE_SIZE, DMA_TO_DEVICE);
 	}
 }
-- 
2.24.0.432.g9d3f5f5b63-goog

Re: [PATCH net] gve: fix dma sync bug where not all pages synced

[Jakub Kicinski]

On Mon, 18 Nov 2019 14:36:30 -0800, Adi Suresh wrote:
> The previous commit "Fixes DMA synchronization" had a bug where the

Please use the standard way of quoting commits.

> last page in the memory range could not be synced. This change fixes
> the behavior so that all the required pages are synced.
> 

Please add a Fixes tag.

> Signed-off-by: Adi Suresh <adisuresh@google.com>
> Reviewed-by: Catherine Sullivan <csully@google.com>
> ---
>  drivers/net/ethernet/google/gve/gve_tx.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/google/gve/gve_tx.c b/drivers/net/ethernet/google/gve/gve_tx.c
> index 0a9a7ee2a866..89271380bbfd 100644
> --- a/drivers/net/ethernet/google/gve/gve_tx.c
> +++ b/drivers/net/ethernet/google/gve/gve_tx.c
> @@ -393,12 +393,12 @@ static void gve_tx_fill_seg_desc(union gve_tx_desc *seg_desc,
>  static void gve_dma_sync_for_device(struct device *dev, dma_addr_t *page_buses,
>  				    u64 iov_offset, u64 iov_len)
>  {
> -	dma_addr_t dma;
> -	u64 addr;
> +	u64 last_page = (iov_offset + iov_len - 1) / PAGE_SIZE;
> +	u64 first_page = iov_offset / PAGE_SIZE;
> +	u64 page;
>  
> -	for (addr = iov_offset; addr < iov_offset + iov_len;
> -	     addr += PAGE_SIZE) {
> -		dma = page_buses[addr / PAGE_SIZE];
> +	for (page = first_page; page <= last_page; page++) {
> +		dma_addr_t dma = page_buses[page];

Empty line after variable declaration. Perhaps keep the dma declaration
outside the loop, since this is a fix the smaller the better.

>  		dma_sync_single_for_device(dev, dma, PAGE_SIZE, DMA_TO_DEVICE);
>  	}
>  }

Re: [PATCH net] gve: fix dma sync bug where not all pages synced

[Adi Suresh]

On Mon, Nov 18, 2019 at 3:19 PM Jakub Kicinski
<jakub.kicinski@netronome.com> wrote:
>
> On Mon, 18 Nov 2019 14:36:30 -0800, Adi Suresh wrote:
> > The previous commit "Fixes DMA synchronization" had a bug where the
>
> Please use the standard way of quoting commits.
>
> > last page in the memory range could not be synced. This change fixes
> > the behavior so that all the required pages are synced.
> >
>
> Please add a Fixes tag.
>
> > Signed-off-by: Adi Suresh <adisuresh@google.com>
> > Reviewed-by: Catherine Sullivan <csully@google.com>
> > ---
> >  drivers/net/ethernet/google/gve/gve_tx.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/google/gve/gve_tx.c b/drivers/net/ethernet/google/gve/gve_tx.c
> > index 0a9a7ee2a866..89271380bbfd 100644
> > --- a/drivers/net/ethernet/google/gve/gve_tx.c
> > +++ b/drivers/net/ethernet/google/gve/gve_tx.c
> > @@ -393,12 +393,12 @@ static void gve_tx_fill_seg_desc(union gve_tx_desc *seg_desc,
> >  static void gve_dma_sync_for_device(struct device *dev, dma_addr_t *page_buses,
> >                                   u64 iov_offset, u64 iov_len)
> >  {
> > -     dma_addr_t dma;
> > -     u64 addr;
> > +     u64 last_page = (iov_offset + iov_len - 1) / PAGE_SIZE;
> > +     u64 first_page = iov_offset / PAGE_SIZE;
> > +     u64 page;
> >
> > -     for (addr = iov_offset; addr < iov_offset + iov_len;
> > -          addr += PAGE_SIZE) {
> > -             dma = page_buses[addr / PAGE_SIZE];
> > +     for (page = first_page; page <= last_page; page++) {
> > +             dma_addr_t dma = page_buses[page];
>
> Empty line after variable declaration. Perhaps keep the dma declaration
> outside the loop, since this is a fix the smaller the better.
>
> >               dma_sync_single_for_device(dev, dma, PAGE_SIZE, DMA_TO_DEVICE);
> >       }
> >  }
>

Comments Addressed in v2