Messages in this thread | | | Date | Thu, 6 Oct 2022 10:35:53 +0300 | Subject | Re: [PATCH 1/2] xen/virtio: Fix n_pages calculation in xen_grant_dma_map(unmap)_page() | From | Xenia Ragiadakou <> |
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On 10/5/22 20:48, Oleksandr Tyshchenko wrote: > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> > > Take page offset into the account when calculating the number of pages > to be granted. > > Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> > Fixes: d6aca3504c7d ("xen/grant-dma-ops: Add option to restrict memory access under Xen") > --- > drivers/xen/grant-dma-ops.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c > index 8973fc1e9ccc..1998d0e8ce82 100644 > --- a/drivers/xen/grant-dma-ops.c > +++ b/drivers/xen/grant-dma-ops.c > @@ -153,7 +153,7 @@ static dma_addr_t xen_grant_dma_map_page(struct device *dev, struct page *page, > unsigned long attrs) > { > struct xen_grant_dma_data *data; > - unsigned int i, n_pages = PFN_UP(size); > + unsigned int i, n_pages = PFN_UP(offset + size);
Here, why do we use PFN_UP and not XEN_PFN_UP? Also, since the variable 'n_pages' seems to refer to the number of grants (unless I got it all entirely wrong ...), wouldn't it be more suitable to call explicitly gnttab_count_grant()? If the above questions have been already answered in the past, please ignore.
> grant_ref_t grant; > dma_addr_t dma_handle; > > @@ -185,7 +185,8 @@ static void xen_grant_dma_unmap_page(struct device *dev, dma_addr_t dma_handle, > unsigned long attrs) > { > struct xen_grant_dma_data *data; > - unsigned int i, n_pages = PFN_UP(size); > + unsigned long offset = dma_handle & (PAGE_SIZE - 1); > + unsigned int i, n_pages = PFN_UP(offset + size); > grant_ref_t grant; > > if (WARN_ON(dir == DMA_NONE))
-- Xenia
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