From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57633) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YH92V-0003hN-2a for qemu-devel@nongnu.org; Fri, 30 Jan 2015 05:43:04 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YH92R-00009F-TD for qemu-devel@nongnu.org; Fri, 30 Jan 2015 05:43:03 -0500 Received: from mail-la0-f47.google.com ([209.85.215.47]:37820) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YH92R-000096-Lr for qemu-devel@nongnu.org; Fri, 30 Jan 2015 05:42:59 -0500 Received: by mail-la0-f47.google.com with SMTP id hz20so22878555lab.6 for ; Fri, 30 Jan 2015 02:42:58 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20150130013610.GB8636@toto> References: <1422557717-19120-1-git-send-email-peter.maydell@linaro.org> <20150130013610.GB8636@toto> From: Peter Maydell Date: Fri, 30 Jan 2015 10:42:38 +0000 Message-ID: Content-Type: text/plain; charset=UTF-8 Subject: Re: [Qemu-devel] [PATCH v2 00/11] target-arm: handle mmu_idx/translation regimes properly List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Edgar E. Iglesias" Cc: Andrew Jones , Greg Bellows , =?UTF-8?B?QWxleCBCZW5uw6ll?= , QEMU Developers , Patch Tracking On 30 January 2015 at 01:36, Edgar E. Iglesias wrote: > IIRC, last time the dedicated S-EL0 and S-EL1 MMU idx came up the > discussion went around flushing the qemu tlbs when switching between > S/NS. Having the dedicated MMU-idx is faster but for Aarch64 I think > we would need logic in at least the TTBRx access handlers to make use > of the dedicated secure MMU idx as Aarch64 secure monitors need to > reprogram the MMU when world switching. > > Another thing around the ARMMMUIdx_S2NS index. > From what I've seen, what would really help is having a fast > way to go from VM mode to non-vm mode. In particular for KVM. > For example when a guest writes to a virtio console there is alot > of ping-ponging between NS-S12(Guest) and NS-S1(Linux/KVM). > > Similary for XEN, it would really help to have that ASID/VMID indexed TLB I > think you suggested at some point. In XEN's case the ping-ponging > goes between two guests, domUs and dom0. Yes, the lack of ASID/VMID restrictions on the TLB hurts us. It's tricky to implement in s/w without it being slower than what we have now, though. > I'm not try to indicate that you should add any of that now, > I'm just not sure sure it's worth adding the ARMMMUIdx_S2NS without > trying if it will actually give any real life improvements in > QEMU. Mostly my aim here was to make sure we were actually treating separately the various virt-to-phys mappings which the architecture says are separate, so we don't have nasty "hit something stale in the TLB" bugs to track down. -- PMM