On Tue, Jun 16, 2020 at 12:09:16PM -0400, Peter Xu wrote: > On Tue, Jun 16, 2020 at 04:49:28PM +0100, Stefan Hajnoczi wrote: > > Isolation between applications is preserved but there is no isolation > > between the device and the application itself. The application needs to > > trust the device. > > > > Examples: > > > > 1. The device can snoop secret data from readable pages in the > > application's virtual memory space. > > > > 2. The device can gain arbitrary execution on the CPU by overwriting > > control flow addresses (e.g. function pointers, stack return > > addresses) in writable pages. > > To me, SVA seems to be that "middle layer" of secure where it's not as safe as > VFIO_IOMMU_MAP_DMA which has buffer level granularity of control (but of course > we pay overhead on buffer setups and on-the-fly translations), however it's far > better than DMA with no IOMMU which can ruin the whole host/guest, because > after all we do a lot of isolations as process based. > > IMHO it's the same as when we see a VM (or the QEMU process) as a whole along > with the guest code. In some cases we don't care if the guest did some bad > things to mess up with its own QEMU process. It is still ideal if we can even > stop the guest from doing so, but when it's not easy to do it the ideal way, we > just lower the requirement to not spread the influence to the host and other > VMs. Makes sense. Stefan
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