From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] KVM: x86: fix vcpu->mmio_fragments overflow Date: Mon, 22 Oct 2012 14:56:42 +0200 Message-ID: <5085428A.9050401@redhat.com> References: <5081033C.4060503@linux.vnet.ibm.com> <20121022091615.GG29310@redhat.com> <50852972.305@linux.vnet.ibm.com> <20121022112314.GO29310@redhat.com> <50852F9C.9020808@siemens.com> <20121022114311.GQ29310@redhat.com> <508531E1.2030307@siemens.com> <508539A8.40404@redhat.com> <50853FF1.8010809@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , Xiao Guangrong , Marcelo Tosatti , LKML , KVM To: Jan Kiszka Return-path: In-Reply-To: <50853FF1.8010809@siemens.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 10/22/2012 02:45 PM, Jan Kiszka wrote: > On 2012-10-22 14:18, Avi Kivity wrote: >> On 10/22/2012 01:45 PM, Jan Kiszka wrote: >> >>>> Indeed. git pull, recheck and call for kvm_flush_coalesced_mmio_buffer() >>>> is gone. So this will break new userspace, not old. By global you mean >>>> shared between devices (or memory regions)? >>> >>> Yes. We only have a single ring per VM, so we cannot flush multi-second >>> VGA access separately from other devices. In theory solvable by >>> introducing per-region rings that can be driven separately. >> >> But in practice unneeded. Real time VMs can disable coalescing and not >> use planar VGA modes. > > A) At least right now, we do not differentiate between the VGA modes and > if flushing is needed. So that device is generally taboo for RT cores of > the VM. In non-planar modes the memory will be direct mapped, which overrides coalescing (since kvm or qemu never see an exit). > B) We need to disable coalescing in E1000 as well - if we want to use > that model. True. -- error compiling committee.c: too many arguments to function