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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58EEAC433FE for ; Mon, 15 Nov 2021 18:58:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 40AFB60EB2 for ; Mon, 15 Nov 2021 18:58:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237999AbhKOTAx (ORCPT ); Mon, 15 Nov 2021 14:00:53 -0500 Received: from mail.kernel.org ([198.145.29.99]:33630 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243307AbhKOS6c (ORCPT ); Mon, 15 Nov 2021 13:58:32 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id EA70663491; Mon, 15 Nov 2021 18:12:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1636999977; bh=u7muo/mGyPVEsoiZHOl5X7P4PEuR9PTtZuoVs3d+uE8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gfmyUL0z6Xza/aOi480BPKetswpzcI1Esesas4UTV7NYTF786IDCIaYfSL3rvDfd9 YFZhLTV13U6AxhRsedvtXKlBGvWRI7SBgfEMdJMWf5zE60ojA17aWYAIQaMAtv5sqS fv7RNVL03Sx6I4iJyK6+ccYMtf1f9GQYx041chpA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ricardo Koller , Jim Mattson , Paolo Bonzini , Sasha Levin Subject: [PATCH 5.14 491/849] KVM: selftests: Fix nested SVM tests when built with clang Date: Mon, 15 Nov 2021 17:59:34 +0100 Message-Id: <20211115165436.891144908@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211115165419.961798833@linuxfoundation.org> References: <20211115165419.961798833@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jim Mattson [ Upstream commit ed290e1c20da19fa100a3e0f421aa31b65984960 ] Though gcc conveniently compiles a simple memset to "rep stos," clang prefers to call the libc version of memset. If a test is dynamically linked, the libc memset isn't available in L1 (nor is the PLT or the GOT, for that matter). Even if the test is statically linked, the libc memset may choose to use some CPU features, like AVX, which may not be enabled in L1. Note that __builtin_memset doesn't solve the problem, because (a) the compiler is free to call memset anyway, and (b) __builtin_memset may also choose to use features like AVX, which may not be available in L1. To avoid a myriad of problems, use an explicit "rep stos" to clear the VMCB in generic_svm_setup(), which is called both from L0 and L1. Reported-by: Ricardo Koller Signed-off-by: Jim Mattson Fixes: 20ba262f8631a ("selftests: KVM: AMD Nested test infrastructure") Message-Id: <20210930003649.4026553-1-jmattson@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- tools/testing/selftests/kvm/lib/x86_64/svm.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/kvm/lib/x86_64/svm.c b/tools/testing/selftests/kvm/lib/x86_64/svm.c index 2ac98d70d02bd..161eba7cd1289 100644 --- a/tools/testing/selftests/kvm/lib/x86_64/svm.c +++ b/tools/testing/selftests/kvm/lib/x86_64/svm.c @@ -54,6 +54,18 @@ static void vmcb_set_seg(struct vmcb_seg *seg, u16 selector, seg->base = base; } +/* + * Avoid using memset to clear the vmcb, since libc may not be + * available in L1 (and, even if it is, features that libc memset may + * want to use, like AVX, may not be enabled). + */ +static void clear_vmcb(struct vmcb *vmcb) +{ + int n = sizeof(*vmcb) / sizeof(u32); + + asm volatile ("rep stosl" : "+c"(n), "+D"(vmcb) : "a"(0) : "memory"); +} + void generic_svm_setup(struct svm_test_data *svm, void *guest_rip, void *guest_rsp) { struct vmcb *vmcb = svm->vmcb; @@ -70,7 +82,7 @@ void generic_svm_setup(struct svm_test_data *svm, void *guest_rip, void *guest_r wrmsr(MSR_EFER, efer | EFER_SVME); wrmsr(MSR_VM_HSAVE_PA, svm->save_area_gpa); - memset(vmcb, 0, sizeof(*vmcb)); + clear_vmcb(vmcb); asm volatile ("vmsave %0\n\t" : : "a" (vmcb_gpa) : "memory"); vmcb_set_seg(&save->es, get_es(), 0, -1U, data_seg_attr); vmcb_set_seg(&save->cs, get_cs(), 0, -1U, code_seg_attr); -- 2.33.0