From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Graf Subject: Re: the arm cache coherency cluster "v2" Date: Sun, 03 May 2015 23:29:54 +0200 Message-ID: <55469352.9000707@suse.de> References: <1426705700-2564-1-git-send-email-drjones@redhat.com> <20150318191819.GB7077@hawk.usersys.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 7EA6C4F75E for ; Sun, 3 May 2015 17:21:20 -0400 (EDT) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id SkF7Qxr+lB4r for ; Sun, 3 May 2015 17:21:18 -0400 (EDT) Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id BF9574F757 for ; Sun, 3 May 2015 17:21:18 -0400 (EDT) In-Reply-To: <20150318191819.GB7077@hawk.usersys.redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: Andrew Jones , kvmarm@lists.cs.columbia.edu, qemu-devel@nongnu.org, ard.biesheuvel@linaro.org, christoffer.dall@linaro.org, marc.zyngier@arm.com, peter.maydell@linaro.org, pbonzini@redhat.com Cc: catalin.marinas@arm.com, lersek@redhat.com List-Id: kvmarm@lists.cs.columbia.edu On 18.03.15 20:18, Andrew Jones wrote: > On Wed, Mar 18, 2015 at 03:08:20PM -0400, Andrew Jones wrote: >> In reply to this message I'll send two series' one for KVM and >> one for QEMU. The two series' are their respective component >> complements, and attempt to implement cache coherency for arm >> guests using emulated devices, where the emulator (qemu) uses >> cached memory for the device memory, but the guest uses >> uncached - as device memory is generally used. Right now I've >> just focused on VGA vram. >> >> This approach is the "MADV_UNCACHED" type that Paolo suggested. >> This type of approach could also be described as "make userspace's >> memory access type match the expected access type of the guest", >> and Mario has suggested using a memory driver, which could have >> the same result. >> >> The coming series' is inspired by both Paolo's and Mario's >> suggestions, but it uses a kvm memslot flag, rather than an >> madvise flag, and thus for the memory driver, it's just KVM. >> >> See the thread >> >> https://lists.gnu.org/archive/html/qemu-devel/2015-03/msg01254.html >> >> for some more background. >> >> Thanks in advance for comments. >> >> drew > > I forgot to mention that I've done some light testing with this. > It seems to work, and without (to eye) noticeable performance > degradation. Just for the record, I couldn't get it to work :). But I'm looking forward to the next version with MMU notifiers! Alex