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=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 8D3FBC433DB for ; Mon, 28 Dec 2020 23:44:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4CA54223C8 for ; Mon, 28 Dec 2020 23:44:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728792AbgL1Xnz (ORCPT ); Mon, 28 Dec 2020 18:43:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727731AbgL1Xnz (ORCPT ); Mon, 28 Dec 2020 18:43:55 -0500 Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 02E3BC0613D6 for ; Mon, 28 Dec 2020 15:43:15 -0800 (PST) Received: by mail-pj1-x102f.google.com with SMTP id lj6so529896pjb.0 for ; Mon, 28 Dec 2020 15:43:14 -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:content-transfer-encoding:in-reply-to; bh=KdY1wS/rYHCSOYMjTfERbDcI4DcnIWo+QIgBl5bB1jk=; b=m3vcS6BdgKS/yXLIAFn813WCIsq5OH+pHCKKlaNiR2DS1+eQ2ZnBLlJjsyVySlR3yd mGWr5lqARNOyxyOxRjMBGktmWPJglvCsXELZiplMlTqm2pvbDBp8dt0H3Lk7TcBUSzUv HRBEQj7W5PE1LdivHNia0mBR4/gAkSyEDZr+CRwzcnNEuPIfRu3lnh3E735i7o31gybX cxDX+LSlBUoA490QABXtbf5jthT/xhjSH+b43QNH/2BXseS3WM3bj9AQ5/qLMPGSCxSj Gk8BxCinLZOrFOSJnKAwvpTcAAMtC8LRO/ZMLyy4rL1oaJpA19B0xbgCZYvxm4L2ztBq 4nCQ== 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:content-transfer-encoding :in-reply-to; bh=KdY1wS/rYHCSOYMjTfERbDcI4DcnIWo+QIgBl5bB1jk=; b=aQ98clSk+OGhRLuIHfeGP10ViqnMttFU2AtLF3B3eFKE9xNgUa00bKAnKmXxw1CA/j TwfEJyBjw4VfaTpYYd5idggBBupp4GfbBlwEDsvTZreOGD1s7HyaWqUiNCsDoPH48YKc YfqClyVnYd6LPiAJGeHmvJR6x+P/EW9h9s4F2cOuPEhf8nGzoYih/dB+V2WgKpEeXuFU 0Qc8V9czbzKrCGzqqFYDQCxyKI70SvppYrM5MdU1SyDQeduBhMgj0c40sxyKB1YOAggv 1pRmrVHrgEPuXnnkkObCK4c6r6HvhM2gf+P9j5A4rogbtfd0k09z2kuIui/mh4cCsJ4R grDQ== X-Gm-Message-State: AOAM531pRchB4BgSWJKFvmcD8SlQimN3wursASgw9IiDgZHDTKOhDJTg T66mMNK7cVcdzKXoZ7/KO33RCg== X-Google-Smtp-Source: ABdhPJxsOfbVzxtX2HuIMp1swW4UR0Sw8DZgM8XhIRjOer9pEP5QBUwuO3Udr/qv3GLZI5avkNyACw== X-Received: by 2002:a17:902:12c:b029:da:e63c:dc92 with SMTP id 41-20020a170902012cb02900dae63cdc92mr46845987plb.71.1609198993698; Mon, 28 Dec 2020 15:43:13 -0800 (PST) Received: from google.com ([2620:15c:f:10:1ea0:b8ff:fe73:50f5]) by smtp.gmail.com with ESMTPSA id 8sm21335103pfz.93.2020.12.28.15.43.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Dec 2020 15:43:13 -0800 (PST) Date: Mon, 28 Dec 2020 15:43:06 -0800 From: Sean Christopherson To: Borislav Petkov Cc: Peter Gonda , Thomas Gleixner , Ingo Molnar , Joerg Roedel , Tom Lendacky , linux-kernel@vger.kernel.org, x86@kernel.org, David Rientjes Subject: Re: [PATCH] x86/sev-es: Fix SEV-ES OUT/IN immediate opcode vc handling Message-ID: References: <20201217010409.3675060-1-pgonda@google.com> <20201228223650.GD20321@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20201228223650.GD20321@zn.tnic> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 28, 2020, Borislav Petkov wrote: > On Thu, Dec 17, 2020 at 09:19:13AM -0800, Sean Christopherson wrote: > > On Wed, Dec 16, 2020, Peter Gonda wrote: > > > > > > The IN and OUT immediate instructions only use an 8-bit immediate. The > > > current VC handler uses the entire 32-bit immediate value. These > > > instructions only set the first bytes. > > > > > > Tested with a loop back port with "outb %0,$0xe0". Before the port seen > > > by KVM was 0xffffffffffffffe0 instead of 0xe0. After the correct port > > > was seen by KVM and the guests loop back OUT then IN were equal. > > > > > > > > > Signed-off-by: Peter Gonda > > > Acked-by: David Rientjes > > > > > > > > > --- > > > arch/x86/kernel/sev-es-shared.c | 8 ++++++-- > > > drivers/Makefile | 1 + > > > 2 files changed, 7 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c > > > index 7d04b356d44d..6c790377c55c 100644 > > > --- a/arch/x86/kernel/sev-es-shared.c > > > +++ b/arch/x86/kernel/sev-es-shared.c > > > @@ -305,14 +305,14 @@ static enum es_result vc_ioio_exitinfo(struct es_em_ctxt *ctxt, u64 *exitinfo) > > > case 0xe4: > > > case 0xe5: > > > *exitinfo |= IOIO_TYPE_IN; > > > - *exitinfo |= (u64)insn->immediate.value << 16; > > > + *exitinfo |= insn->immediate.bytes[0] << 16; > > > > Can't we just drop the explicit cast to u64? Or explicitly cast to u8? Doesn't > > really matter, but poking into the backing bytes feels a bit backwards. > > GHCB spec says for IOIO_PROT (exit code 0x7b): > > "SW_EXITINFO1 will be set as documented in AMD64 Architecture > Programmer’s Manual Volume 2: System Programming, Section 15.10.2" > > That section has "Figure 15-2. EXITINFO1 for IOIO Intercept" where > [31:16] is the intercepted I/O port. > > Now, insn->immediate.value is a union between a signed int and a > unsigned char bytes[4] array so in order to be absolutely correct, that > should use: > > insn->immediate.bytes[0] Eh, casting to u8 is "absolutely correct" as well. I don't like using bytes[] because it feels like accessing the raw data as opposed to the end result of decoding, but it's not a sticking point. > (u64) cast doesn't matter because *exitinfo = 0 at function entry and > that is part of the first assignment afterwards. > > I still don't see how that sign extension 0xffffffffffffffe0 can happen, > though. Maybe something gets added during instruction decoding... Yes, insn_get_immediate() sets insn->immediate.value directly and sign extends the imm8 (which is correct, e.g. for "AND r/m64, imm8"). switch (inat_immediate_size(insn->attr)) { case INAT_IMM_BYTE: insn->immediate.value = get_next(signed char, insn); insn->immediate.nbytes = 1; break; ... } > > Hmmm. > > -- > Regards/Gruss, > Boris. > > https://people.kernel.org/tglx/notes-about-netiquette