From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthias Ehrenfeuchter Subject: AMD Ryzen KVM/NPT/IOMMU issue Date: Wed, 3 May 2017 16:37:31 +0200 Message-ID: <575f8fbc-0fdc-f336-e3da-53f27da4b2e1@markju.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: iommu@lists.linux-foundation.org Hi, There are a lot of messages/threads out there about bad performance while using AMDs Ryzen with KVM GPU passthrough. It revolves all on enabling/disabling npt, while enabled overall VM performance is nice but the GPU performance gives me about 20% (and a lot of drops to zero GPU usage, while CPU/Disk/Ram also doing nothing) compared to npt disabled. But while npt is disabled overall VM performance is like beeing on 4x86 with floppy disk as only storage. (Ex. it takes 2 seconds just to open startmenu while host and vm are in idle, and neither CPU pinning, changing CPU model, changing storage device nor using hugepages changed anything). So everything I read pointed to a bug in the npt implementation? Anything I could do to get closer to the "thing" issuing this? Best Regards efeu