From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [Qemu-devel] Re: QEMU-KVM and video performance Date: Wed, 21 Apr 2010 23:51:43 +0300 Message-ID: <4BCF655F.1080602@redhat.com> References: <4BCEBE5C.4020404@redhat.com> <20100421100840.GF13114@shareable.org> <4BCED82C.9020702@redhat.com> <20100421183930.GL27575@shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gerhard Wiesinger , qemu-devel@nongnu.org, kvm@vger.kernel.org To: Jamie Lokier Return-path: Received: from mx1.redhat.com ([209.132.183.28]:2134 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756555Ab0DUUvv (ORCPT ); Wed, 21 Apr 2010 16:51:51 -0400 In-Reply-To: <20100421183930.GL27575@shareable.org> Sender: kvm-owner@vger.kernel.org List-ID: On 04/21/2010 09:39 PM, Jamie Lokier wrote: > Avi Kivity wrote: > >> Writes to vga in 16-color mode don't change set a memory location to a >> value, instead they change multiple memory locations. >> > While code is just writing to the VGA memory, not reading(*) and not > touching the VGA I/O register that control the write latches, is it > possible in principle to swizzle the format around in memory to make > regular writes work? > Not in software. We can map pages, not cross address lines. > (*) Reading should be ok for some settings of the write latches, I > think. > > I wonder if guests of interest behave like that. > Guests that use 16 color vga are usually of little interest. >>> Is this a case where TCG would run significantly faster for code blocks >>> that have been detected to access the VGA memory? >>> >> Yes. >> > $ date > Wed Apr 21 19:37:38 2015 > $ modprobe ktcg > That's why the vmware software vmm was faster than the hardware vmm for the initial iterations of vmx. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.