Am 09.01.2018 um 16:18 schrieb Fabian Grünbichler: > On Tue, Jan 09, 2018 at 02:58:24PM +0100, Fabian Grünbichler wrote: >> On Mon, Jan 08, 2018 at 09:34:57PM +0100, Stefan Priebe - Profihost AG wrote: >>> Hello, >>> >>> for meltdown mitigation and performance it's important to have the pcid >>> flag passed down to the guest (f.e. >>> https://groups.google.com/forum/m/#!topic/mechanical-sympathy/L9mHTbeQLNU). >>> >>> My host shows the flag: >>> # grep ' pcid ' /proc/cpuinfo | wc -l >>> 56 >>> >>> But the guest does not: >>> # grep pcid /proc/cpuinfo >>> # >>> >>> Guest was started with: >>> -cpu IvyBridge,+kvm_pv_unhalt,+kvm_pv_eoi,enforce,vendor=GenuineIntel >>> >>> Is this something missing in host kernel or in PVE? >>> >>> Greets, >>> Stefan >> >> we are preparing a patch for qemu-server to allow enabling the pcid >> cpuflag on a VM config level (especially since most VMs will run with >> kvm64, where changing the default is not an option!). >> >> switching it on by default for SandyBridge and co (which are missing it >> in Qemu, but support it technically) will likely happen with the move to >> Qemu 2.11, pending further feedback and review (it is not clear at all >> how various guest OS handle getting the flag changed out under them when >> migrating, and we don't want to integrate specific pinning support in a >> rushed through manner). >> >> for now you can of course just patch a hardcoded +pcid in to the cpu >> flag list on your hosts if you know your CPUs all support it and >> stop/start your VMs to regain lost performance. >> > > should be on pvetest for 5.x and 4.x shortly - please provide feedback! > > patches for exposing it somewhere on the GUI will follow (most likely > tomorrow).
Thanks! I would love to see it as a default for the specific qemu cpu models. I mean we know exactly that sandybridge, ivybridge, ... support it or not? Greets, Stefan _______________________________________________ pve-devel mailing list pve-devel@pve.proxmox.com https://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
