Re: [PATCH V2] Xen: ARM: Zero reserved fields of xatp before making hypervisor call

From: Juergen Gross
Date: Mon Jan 02 2017 - 01:13:47 EST


On 28/12/16 01:47, Jiandi An wrote:
> Ensure all reserved fields of xatp are zero before making
> hypervisor call to XEN in xen_map_device_mmio().
> xenmem_add_to_physmap_one() in XEN fails the mapping request if
> extra.res reserved field in xatp is not zero for XENMAPSPACE_dev_mmio
> request.
>
> Signed-off-by: Jiandi An <anjiandi@xxxxxxxxxxxxxx>
> ---
> Changed zeroing xatp to a static initialization
> of .domid and .space for xatp.
>
> drivers/xen/arm-device.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/xen/arm-device.c b/drivers/xen/arm-device.c
> index 778acf8..85dd20e 100644
> --- a/drivers/xen/arm-device.c
> +++ b/drivers/xen/arm-device.c
> @@ -58,9 +58,13 @@ static int xen_map_device_mmio(const struct resource *resources,
> xen_pfn_t *gpfns;
> xen_ulong_t *idxs;
> int *errs;
> - struct xen_add_to_physmap_range xatp;
>
> for (i = 0; i < count; i++) {
> + struct xen_add_to_physmap_range xatp = {
> + .domid = DOMID_SELF,
> + .space = XENMAPSPACE_dev_mmio
> + };
> +

I still don't see the need to re-initialize the input parts of xatp
on each loop iteration unless you can show the need for it (e.g. a
buggy hypervisor version not conforming to the interface specification).

OTOH I don't feel really strong about it and let Stefano being the
maintainer for the ARM parts decide.


Juergen

> r = &resources[i];
> nr = DIV_ROUND_UP(resource_size(r), XEN_PAGE_SIZE);
> if ((resource_type(r) != IORESOURCE_MEM) || (nr == 0))
> @@ -87,9 +91,7 @@ static int xen_map_device_mmio(const struct resource *resources,
> idxs[j] = XEN_PFN_DOWN(r->start) + j;
> }
>
> - xatp.domid = DOMID_SELF;
> xatp.size = nr;
> - xatp.space = XENMAPSPACE_dev_mmio;
>
> set_xen_guest_handle(xatp.gpfns, gpfns);
> set_xen_guest_handle(xatp.idxs, idxs);
>