> Subject: Re: [EXTERNAL] Re: [PATCH v2 0/2] vhost-vdpa: Add support for NO- > IOMMU mode > > On Wed, Nov 06, 2024 at 12: 38: 02PM +0000, Srujana Challa wrote: > It is > going in circles, let me give the summary, > Issue: We need to address the lack > of no-IOMMU support in the vhost vDPA driver for better performance. > > Measured > On Wed, Nov 06, 2024 at 12:38:02PM +0000, Srujana Challa wrote: > > It is going in circles, let me give the summary, > > Issue: We need to address the lack of no-IOMMU support in the vhost vDPA > driver for better performance. > > Measured Performance: On the machine "13th Gen Intel(R) Core(TM) > > i9-13900K, 32 Cores", we observed > > Looks ike you are going in circles indeed. Lack of performance is never a > reason to disable the basic memoy safety for userspace drivers. If security is a priority, the IOMMU should stay enabled. In that case, this patch wouldn’t cause any issues, right? > > The (also quite bad) reason why vfio-nummu was added was to support > hardware entirely with an iommu. > > There is absolutely no reason to add krnel code for new methods of unsafer > userspace I/O without an IOMMU ever.
