On Thu, May 13, 2021 at 10:08:28AM +0800, liulongfang wrote:
> On 2021/5/12 20:10, Jason Gunthorpe wrote:
> > On Wed, May 12, 2021 at 04:39:43PM +0800, liulongfang wrote:
> >> Therefore, this method of limiting the length of the BAR
> >> configuration space can prevent unsafe operations of the memory.
> > The issue is DMA controlled by the guest accessing the secure BAR
> > area, not the guest CPU.
> > Jason
> > .
> This secure BAR area is not presented to the Guest,
> which makes it impossible for the Guest to obtain the secure BAR area
> when establishing the DMA mapping of the configuration space.
> If the DMA controller accesses the secure BAR area, the access will
> be blocked by the SMMU.
There are scenarios where this is not true.
At a minimum the mdev driver should refuse to work in those cases.