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Re: [PATCH v2 1/2] xen: don't allow gnttab_dma_[alloc|free]_pages() in PV guest
- To: Juergen Gross <jgross@xxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Tue, 10 Nov 2026 09:59:53 +0000
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 10 Nov 2026 10:00:06 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 10/11/2026 9:56 am, Juergen Gross wrote:
> Today gnttab_dma_alloc_pages() or gnttab_dma_free_pages are never
> called when running as a PV guest, but this holds for in-tree callers
> only.
>
> Bail out early when being called in PV mode in order to ensure no out
> of tree module or future use cases are violating this assumption.
>
> This enables to safely remove PV-only code from both functions.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
> drivers/xen/grant-table.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index 604c4eea5930..56a497987942 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -1063,6 +1063,9 @@ int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args
> *args)
> size_t size;
> int i, ret;
>
> + if (WARN_ON(xen_pv_domain()))
> + return -EINVAL;
This will get very spammy if hit. WARN_ON_ONCE() ?
~Andrew
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