From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Fedin Subject: RE: [PATCH v4 0/4] KVM: arm64: BUG FIX: Correctly handle zero register transfers Date: Tue, 08 Dec 2015 09:57:21 +0300 Message-ID: <009501d13185$b02d1150$108733f0$@samsung.com> References: <20151205003334.GB3117@hawk.localdomain> <011601d130ca$64cc9070$2e65b150$@samsung.com> <20151207223631.GJ4402@hawk.localdomain> <20151207234555.GA2980@hawk.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, 'Marc Zyngier' To: 'Andrew Jones' Return-path: Received: from mailout2.w1.samsung.com ([210.118.77.12]:51842 "EHLO mailout2.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932460AbbLHG5Z (ORCPT ); Tue, 8 Dec 2015 01:57:25 -0500 Received: from eucpsbgm2.samsung.com (unknown [203.254.199.245]) by mailout2.w1.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0NZ10005U1ZN5N10@mailout2.w1.samsung.com> for kvm@vger.kernel.org; Tue, 08 Dec 2015 06:57:23 +0000 (GMT) In-reply-to: <20151207234555.GA2980@hawk.localdomain> Content-language: ru Sender: kvm-owner@vger.kernel.org List-ID: Hello! > I messed up the "load into xzr" test royally in the last attached patch. > It was quite wrong. Yes, because "mov %0, xzr" is not trapped. > I have now tested > > asm volatile( > "str %3, [%1]\n\t" > "ldr wzr, [%1]\n\t" > "str wzr, [%2]\n\t" > "ldr %0, [%2]\n\t" > :"=r"(val):"r"(addr), "r"(addr2), "r"(0x55555555):"memory"); > report("mmio: 'ldr wzr' check: read 0x%08lx", val != 0x55555555, val); > > which passes I guess i forgot to mention that both addr and addr2 have to be MMIO registers. If they are plain memory, then of course everything will work because they are not trapped. > Anyway, I > probably won't clean this test up and post it. I don't think we really > need to add it as a regression test, unless others disagree and would > like to see it added. Considering how difficult it was to find this problem, and how tricky and unobvious it is, i would ask to add this test. Especially considering you've already written it. At least it will serve as a reminder about the problem. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia