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: Mon, 07 Dec 2015 11:36:28 +0300 Message-ID: <011601d130ca$64cc9070$2e65b150$@samsung.com> References: <20151205003334.GB3117@hawk.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: 'Marc Zyngier' , kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org To: 'Andrew Jones' Return-path: In-reply-to: <20151205003334.GB3117@hawk.localdomain> Content-language: ru 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 List-Id: kvm.vger.kernel.org Hello! > FYI, I tried writing test cases for this issue with kvm-unit-tests. The > issue didn't reproduce for me. It's quite possible my test cases are > flawed, so I'm not making any claims about the validity of the series This is indeed very interesting, so i'll take a look at it. For now i've just only took a quick glance at the code, and i have at least one suggestion. Could you happen to have sp == 0 in check_xzr_sysreg()? In this case it will magically work. Also, you could try to write a test which tries to overwrite xzr. Something like: volatile int *addr1; volatile int *addr2; asm volatile("str %3, [%1]\n\t" "ldr wzr, [%1]\n\t" "str wzr, [%2]\n\t", "ldr %0, [%2]\n\t" :"=r"(res):"r"(addr1), "r"(addr2), "r"(some_nonzero_val):"memory"); Then check for res == some_nonzero_val. If they are equal, you've got the bug :) Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia