On Wed, 2008-07-30 at 14:17 +0100, Diego Ongaro wrote:
> gnttab_setup_table should set an error status code if the gmfn it gets
> for a grant table page is invalid.
>
> I ran into this issue when I tried to set up the grant table during hvm
> domain creation, and it caused a BUG_ON later down the line. With this
> patch, the hypercall will gracefully fail instead.
Do you use 32bit guest on top of 64bit hypervisor? In that case
op.frame_list has different size in the hypervisor and the guest, and
the BUG_ON is probably triggered because of the hypervisor ruining the
stack.
Just curious, but why we want to call setup_table in HVM in the first
place. Since HVM has its isolated address space, it will always fail. It
seems that setup_table is added to HVM because of this:
http://lists.xensource.com/archives/html/xen-devel/2008-03/msg00927.html
At that time, calling setup_table is a guest bug and I think it's already
fixed by removing that call.
So, can we:
1. let setup_table return -ENOSYS again in HVM? or
2. call something like compat_grant_table_op instead in 32/64? or
2. add a stub in hvm_grant_table_op so that it doesn't bother calling
{do,compat}_grant_table_op at all?
Thanks,
Qing
>
> Signed-off-by: Diego Ongaro <diego.ongaro@xxxxxxxxxx>
> ---
> diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -913,8 +913,15 @@ gnttab_setup_table(
> op.status = GNTST_okay;
> for ( i = 0; i < op.nr_frames; i++ )
> {
> gmfn = gnttab_shared_gmfn(d, d->grant_table, i);
> + if ( gmfn == -1 )
> + {
> + gdprintk(XENLOG_INFO,
> + "grant table gmfn unavailable\n");
> + op.status = GNTST_general_error;
> + goto out3;
> + }
> (void)copy_to_guest_offset(op.frame_list, i, &gmfn, 1);
> }
>
> out3:
>
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