Re: [PATCH] xen/virtio: Convert PAGE_SIZE/PAGE_SHIFT/PFN_UP to Xen counterparts

From: Juergen Gross
Date: Fri Oct 07 2022 - 00:46:59 EST

On 06.10.22 23:13, Oleksandr Tyshchenko wrote:

On 06.10.22 20:59, Xenia Ragiadakou wrote:

Hello Xenia

On 10/6/22 15:09, Oleksandr Tyshchenko wrote:
From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

Although XEN_PAGE_SIZE is equal to PAGE_SIZE (4KB) for now, it would
be more correct to use Xen specific #define-s as XEN_PAGE_SIZE can
be changed at some point in the future.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>


So, the calculated number of grants may differ.

Good point, I think you are right, so we need to additionally use
xen_offset_in_page() macro in xen_grant_dma_map_page(),

something like that to be squashed with current patch:

diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
index 9d5eca6d638a..bb984dc05deb 100644
--- a/drivers/xen/grant-dma-ops.c
+++ b/drivers/xen/grant-dma-ops.c
@@ -169,7 +169,7 @@ 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 = XEN_PFN_UP(offset + size);
+       unsigned int i, n_pages = XEN_PFN_UP(xen_offset_in_page(offset)
+ size);

I'd rather introduce another local variable "xen_offset", as it is used

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