From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69B66C432C2 for ; Wed, 25 Sep 2019 13:12:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4832920640 for ; Wed, 25 Sep 2019 13:12:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406197AbfIYNMt (ORCPT ); Wed, 25 Sep 2019 09:12:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49858 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405921AbfIYNMs (ORCPT ); Wed, 25 Sep 2019 09:12:48 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 061A230860DA; Wed, 25 Sep 2019 13:12:48 +0000 (UTC) Received: from vitty.brq.redhat.com (unknown [10.43.2.155]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1FD7E5C1D4; Wed, 25 Sep 2019 13:12:43 +0000 (UTC) From: Vitaly Kuznetsov To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Sean Christopherson , Jim Mattson , Thomas Huth , Andrew Jones , Cornelia Huck Subject: [PATCH] KVM: selftests: fix ucall on x86 Date: Wed, 25 Sep 2019 15:12:42 +0200 Message-Id: <20190925131242.29986-1-vkuznets@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Wed, 25 Sep 2019 13:12:48 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After commit e8bb4755eea2("KVM: selftests: Split ucall.c into architecture specific files") selftests which use ucall on x86 started segfaulting and apparently it's gcc to blame: it "optimizes" ucall() function throwing away va_start/va_end part because it thinks the structure is not being used. Previously, it couldn't do that because the there was also MMIO version and the decision which particular implementation to use was done at runtime. With older gccs it's possible to solve the problem by adding 'volatile' to 'struct ucall' but at least with gcc-8.3 this trick doesn't work. 'memory' clobber seems to do the job. Signed-off-by: Vitaly Kuznetsov --- s390 should, in theory, have the same problem. Thomas, Cornelia, could you please take a look? Thanks! --- tools/testing/selftests/kvm/lib/x86_64/ucall.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/kvm/lib/x86_64/ucall.c b/tools/testing/selftests/kvm/lib/x86_64/ucall.c index 4bfc9a90b1de..da4d89ad5419 100644 --- a/tools/testing/selftests/kvm/lib/x86_64/ucall.c +++ b/tools/testing/selftests/kvm/lib/x86_64/ucall.c @@ -32,7 +32,7 @@ void ucall(uint64_t cmd, int nargs, ...) va_end(va); asm volatile("in %[port], %%al" - : : [port] "d" (UCALL_PIO_PORT), "D" (&uc) : "rax"); + : : [port] "d" (UCALL_PIO_PORT), "D" (&uc) : "rax", "memory"); } uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc) -- 2.20.1