Re: [Xen-devel] [PATCH] vt-d: fix wrong addr in IOTLB invalidation descriptor

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Zhang, Yang Z writes ("[Xen-devel] [PATCH] vt-d: fix wrong addr in IOTLB 
invalidation descriptor"):
> According to vt-d specs, the addr in IOTLB invalidation descriptor should be 
> 4K page aligned.
> 
> Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
> 
> diff -r 0455d8317631 xen/drivers/passthrough/vtd/qinval.c
> --- a/xen/drivers/passthrough/vtd/qinval.c      Thu Jun 28 18:43:28 2012 +0100
> +++ b/xen/drivers/passthrough/vtd/qinval.c      Wed Jul 11 08:43:24 2012 +0800
> @@ -140,7 +140,7 @@ static int gen_iotlb_inv_dsc(struct iomm
>      qinval_entry->q.iotlb_inv_dsc.hi.am = am;
>      qinval_entry->q.iotlb_inv_dsc.hi.ih = ih;
>      qinval_entry->q.iotlb_inv_dsc.hi.res_1 = 0;
> -    qinval_entry->q.iotlb_inv_dsc.hi.addr = addr;
> +    qinval_entry->q.iotlb_inv_dsc.hi.addr = addr >> PAGE_SHIFT_4K;
> 
>      unmap_vtd_domain_page(qinval_entries);
>      spin_unlock_irqrestore(&qi_ctrl->qinval_lock, flags);

Does this mean that previously we were invalidating the wrong place
and therefore our invalidations were ineffective ?  Can this be
exploited somehow by a malicious guest ?

Ian.

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