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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,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 B64D0C433E0 for ; Sat, 9 Jan 2021 05:48:51 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EB82023A01 for ; Sat, 9 Jan 2021 05:48:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EB82023A01 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=yadro.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:51114 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ky77J-00039M-Km for qemu-devel@archiver.kernel.org; Sat, 09 Jan 2021 00:48:49 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:51910) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ky76c-0002k5-34 for qemu-devel@nongnu.org; Sat, 09 Jan 2021 00:48:07 -0500 Received: from mta-02.yadro.com ([89.207.88.252]:35458 helo=mta-01.yadro.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ky76Y-0004KO-Jq for qemu-devel@nongnu.org; Sat, 09 Jan 2021 00:48:05 -0500 Received: from localhost (unknown [127.0.0.1]) by mta-01.yadro.com (Postfix) with ESMTP id A70FB41243; Sat, 9 Jan 2021 05:48:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=yadro.com; h= in-reply-to:content-disposition:content-type:content-type :mime-version:references:message-id:subject:subject:from:from :date:date:received:received:received; s=mta-01; t=1610171279; x=1611985680; bh=7HEB4QCbWTzhKwXIEI+tMmd0zrWMIH9Pm7PlAO1S37A=; b= TJXCH95z/z48C5wuoACVI1gnnEs66sy8E5h8qyXlSEHe3fwo3hDSvnkIL4oOXMfQ BfWt6KD83pFn6q7pRDuxPkfy9MDQhuYvySN6Df+18NSYG4xvfXFsoyQJ7A6sWMzo 7BQ4xGm/N+E+CZjfssSm99TN8I1Y3ISLnS04VBHueLM= X-Virus-Scanned: amavisd-new at yadro.com Received: from mta-01.yadro.com ([127.0.0.1]) by localhost (mta-01.yadro.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id VgXjjWWz8GOs; Sat, 9 Jan 2021 08:47:59 +0300 (MSK) Received: from T-EXCH-03.corp.yadro.com (t-exch-03.corp.yadro.com [172.17.100.103]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mta-01.yadro.com (Postfix) with ESMTPS id 1DE9141203; Sat, 9 Jan 2021 08:47:59 +0300 (MSK) Received: from localhost (172.17.204.212) by T-EXCH-03.corp.yadro.com (172.17.100.103) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P384) id 15.1.669.32; Sat, 9 Jan 2021 08:47:58 +0300 Date: Sat, 9 Jan 2021 08:48:19 +0300 From: Roman Bolshakov To: Hill Ma Subject: Re: [PATCH] hvf: guard xgetbv call. Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-Originating-IP: [172.17.204.212] X-ClientProxiedBy: T-EXCH-01.corp.yadro.com (172.17.10.101) To T-EXCH-03.corp.yadro.com (172.17.100.103) Received-SPF: pass client-ip=89.207.88.252; envelope-from=r.bolshakov@yadro.com; helo=mta-01.yadro.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, dirty@apple.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Dec 18, 2020 at 06:13:47PM -0800, Hill Ma wrote: > This prevents illegal instruction on cpus do not support xgetbv. > > Buglink: https://bugs.launchpad.net/qemu/+bug/1758819 > Signed-off-by: Hill Ma > --- > target/i386/hvf/x86_cpuid.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > Hi Hill, I'm sorry for delay with the review. > diff --git a/target/i386/hvf/x86_cpuid.c b/target/i386/hvf/x86_cpuid.c > index a6842912f5..b4b7111fc3 100644 > --- a/target/i386/hvf/x86_cpuid.c > +++ b/target/i386/hvf/x86_cpuid.c > @@ -100,11 +100,16 @@ uint32_t hvf_get_supported_cpuid(uint32_t func, uint32_t idx, > break; > case 0xD: > if (idx == 0) { > - uint64_t host_xcr0 = xgetbv(0); > - uint64_t supp_xcr0 = host_xcr0 & (XSTATE_FP_MASK | XSTATE_SSE_MASK | > + uint64_t supp_xcr0 = XSTATE_FP_MASK | XSTATE_SSE_MASK | > XSTATE_YMM_MASK | XSTATE_BNDREGS_MASK | > XSTATE_BNDCSR_MASK | XSTATE_OPMASK_MASK | > - XSTATE_ZMM_Hi256_MASK | XSTATE_Hi16_ZMM_MASK); > + XSTATE_ZMM_Hi256_MASK | XSTATE_Hi16_ZMM_MASK; > + if ((ecx & CPUID_EXT_AVX) && > + (ecx & CPUID_EXT_XSAVE) && > + (ecx & CPUID_EXT_OSXSAVE)) { It's sufficient to check only CPUID_EXT_OSXSAVE to ensure xgetbv presence (per SDM Vol. 1 13-5): Software operating with CPL > 0 may need to determine whether the XSAVE feature set and certain XSAVE-enabled features have been enabled. If CPL > 0, execution of the MOV from CR4 instruction causes a general-protection fault (#GP). The following alternative mechanisms allow software to discover the enabling of the XSAVE feature set regardless of CPL: * The value of CR4.OSXSAVE is returned in CPUID.1:ECX.OSXSAVE[bit 27]. If software determines that CPUID.1:ECX.OSXSAVE = 1, the processor supports the XSAVE feature set and the feature set has been enabled in CR4. * Executing the XGETBV instruction with ECX = 0 returns the value of XCR0 in EDX:EAX. XGETBV can be executed if CR4.OSXSAVE = 1 (if CPUID.1:ECX.OSXSAVE = 1), regardless of CPL. > + uint64_t host_xcr0 = xgetbv(0); > + supp_xcr0 &= host_xcr0; > + } > eax &= supp_xcr0; I think instead of the patch you can do: - if (idx == 0) { + if (idx == 0 && (ecx & CPUID_EXT_OSXSAVE)) { That'd keep host values returned from CPUID on platforms that don't support XSAVE. Thanks, Roman > } else if (idx == 1) { > hv_vmx_read_capability(HV_VMX_CAP_PROCBASED2, &cap); > -- > 2.20.1 (Apple Git-117) >