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=-26.1 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_IN_DEF_DKIM_WL 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 3ADAFC433E6 for ; Mon, 21 Dec 2020 18:12:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0AF7723122 for ; Mon, 21 Dec 2020 18:12:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726603AbgLUSMc (ORCPT ); Mon, 21 Dec 2020 13:12:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49986 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726480AbgLUSMc (ORCPT ); Mon, 21 Dec 2020 13:12:32 -0500 Received: from mail-pg1-x530.google.com (mail-pg1-x530.google.com [IPv6:2607:f8b0:4864:20::530]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8130C061285 for ; Mon, 21 Dec 2020 10:11:51 -0800 (PST) Received: by mail-pg1-x530.google.com with SMTP id g18so6800664pgk.1 for ; Mon, 21 Dec 2020 10:11:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=bOLplW+5pp4JzOv86AiZeqRbE94ulVTnl+pKmMDmJSY=; b=HFWrQ9mvEZW6tq7gtcoW2W6O1cpRXIGiH7jNwK3Ivwz/2zIGkq9l678qT9/RTsTR4+ rItrhVmzPjQ2w0Yg+izh2swEM4bjuu8ijBXO45WGBF2ARYlueahJHDb4A/8AYANw6fvT Gre+GIq7Ivj8wjoeIrWS2uhywzjU2dL7uCatGwBOLNsRVtRMwr4i5CeMfRWWio1ohGYG f6P9Mb3+AJI2jgHOcmveCnMPmKz95m3SX6vcIxhXSwIxNDl2fi8Y3rQLho4y9vTBzvJT /cVTftNX5dEHmdWPo+Dg6PqABaa8slheL5lY7yXey9mUqeszVoUfSypa64MjKyjBCgmx kmIA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=bOLplW+5pp4JzOv86AiZeqRbE94ulVTnl+pKmMDmJSY=; b=hMc48iPxg+Xh9dJ3KyQk48qr6hso0ni7NuogRo+i1Jy9sxYB66S57kw9LudwsZniXO D/3uUGv30jz+AWZFH4BUZRBwezQIKhBRWb6pUyeQXZA4EmYSiiXcXpYVwze0mRUCbOWg X1TQhhY3hxWP3jDexGrv2/uqFh2wiMftHsQBgpSCNC5WuGiDREkMjKTThV1C2cbhvUdx TYc4SzpuX0818IveXIAeGzL8d8prsxaG53oeLhfeyu6JZtlm5+LcTp5VRAl/aCWLrl37 oHJg8z4DiPwNzc3ryRvAWAHgATrS5tDTnHEtPJ3YIHq71r4RFvzthZVxsvgFV7lm9dzH IkcA== X-Gm-Message-State: AOAM531Ah8qeuYcr2DQf8MFX5ZwDicMg54RsuXPg/eR2uvL9ADKVonVn +OeBb9jey6jEgTkC78pLg4+QUClQ4wctsg== X-Google-Smtp-Source: ABdhPJzoQsNIctzyZlXh2aS6dXgzLjXlPRuPIlOiMY/6q2NocJbmuerTxlGVGSP70Q2xmfv0qYogTw== X-Received: by 2002:a63:2b42:: with SMTP id r63mr15934021pgr.316.1608572898493; Mon, 21 Dec 2020 09:48:18 -0800 (PST) Received: from google.com ([2620:15c:f:10:1ea0:b8ff:fe73:50f5]) by smtp.gmail.com with ESMTPSA id 82sm17865501pfv.117.2020.12.21.09.48.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Dec 2020 09:48:17 -0800 (PST) Date: Mon, 21 Dec 2020 09:48:10 -0800 From: Sean Christopherson To: Nathan Chancellor Cc: Paolo Bonzini , Tom Lendacky , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Nick Desaulniers , Sami Tolvanen Subject: Re: [PATCH] KVM: SVM: Add register operand to vmsave call in sev_es_vcpu_load Message-ID: References: <20201219063711.3526947-1-natechancellor@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201219063711.3526947-1-natechancellor@gmail.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Dec 18, 2020, Nathan Chancellor wrote: > When using LLVM's integrated assembler (LLVM_IAS=1) while building > x86_64_defconfig + CONFIG_KVM=y + CONFIG_KVM_AMD=y, the following build > error occurs: > > $ make LLVM=1 LLVM_IAS=1 arch/x86/kvm/svm/sev.o > arch/x86/kvm/svm/sev.c:2004:15: error: too few operands for instruction > asm volatile(__ex("vmsave") : : "a" (__sme_page_pa(sd->save_area)) : "memory"); > ^ > arch/x86/kvm/svm/sev.c:28:17: note: expanded from macro '__ex' > #define __ex(x) __kvm_handle_fault_on_reboot(x) > ^ > ./arch/x86/include/asm/kvm_host.h:1646:10: note: expanded from macro '__kvm_handle_fault_on_reboot' > "666: \n\t" \ > ^ > :2:2: note: instantiated into assembly here > vmsave > ^ > 1 error generated. > > This happens because LLVM currently does not support calling vmsave > without the fixed register operand (%rax for 64-bit and %eax for > 32-bit). This will be fixed in LLVM 12 but the kernel currently supports > LLVM 10.0.1 and newer so this needs to be handled. > > Add the proper register using the _ASM_AX macro, which matches the > vmsave call in vmenter.S. There are also two instances in tools/testing/selftests/kvm/lib/x86_64/svm.c that likely need to be fixed. > Fixes: 861377730aa9 ("KVM: SVM: Provide support for SEV-ES vCPU loading") > Link: https://reviews.llvm.org/D93524 > Link: https://github.com/ClangBuiltLinux/linux/issues/1216 > Signed-off-by: Nathan Chancellor > --- > arch/x86/kvm/svm/sev.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index e57847ff8bd2..958370758ed0 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -2001,7 +2001,7 @@ void sev_es_vcpu_load(struct vcpu_svm *svm, int cpu) > * of which one step is to perform a VMLOAD. Since hardware does not > * perform a VMSAVE on VMRUN, the host savearea must be updated. > */ > - asm volatile(__ex("vmsave") : : "a" (__sme_page_pa(sd->save_area)) : "memory"); > + asm volatile(__ex("vmsave %%"_ASM_AX) : : "a" (__sme_page_pa(sd->save_area)) : "memory"); I vote to add a helper in svm.h to encode VMSAVE, even if there is only the one user. Between the rAX behavior (it _must_ be rAX) and taking the HPA of the VMCB, the semantics of VMSAVE are just odd enough to cause a bit of head scratching when reading the code for the first time. E.g. something like: void vmsave(struct page *vmcb) { /* * VMSAVE takes the HPA of a VMCB in rAX (hardcoded by VMSAVE itself). * The _ASM_AX operand is required to specify the address size, which * means VMSAVE cannot consume a 64-bit address outside of 64-bit mode. */ hpa_t vmcb_pa = __sme_page_pa(vmcb); BUG_ON(!IS_ENABLED(CONFIG_X86_64) && (vmcb_pa >> 32)); asm volatile(__ex("vmsave %%"_ASM_AX) : : "a" (vmcb_pa) : "memory"); } > > /* > * Certain MSRs are restored on VMEXIT, only save ones that aren't > -- > 2.30.0.rc0 >