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 DBED3C433E6 for ; Mon, 28 Dec 2020 22:58:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A4A4F2222A for ; Mon, 28 Dec 2020 22:58:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732231AbgL1W4c (ORCPT ); Mon, 28 Dec 2020 17:56:32 -0500 Received: from mail.skyhub.de ([5.9.137.197]:38262 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729646AbgL1Whh (ORCPT ); Mon, 28 Dec 2020 17:37:37 -0500 Received: from zn.tnic (p200300ec2f07e40057167202136ef09a.dip0.t-ipconnect.de [IPv6:2003:ec:2f07:e400:5716:7202:136e:f09a]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id C75CC1EC03CF; Mon, 28 Dec 2020 23:36:55 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1609195015; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tSgkfnt/UUQvT/KFBsvO/zmoogVrWDacpZ6DI9jEwds=; b=ZxXMghFnydpnNENMksdGavQD2HydkvIiYYBVjV9WiPF7fAp5DRon05Gpog+NDfSP2futZ1 r+o6ezqycG7bl5oVkhwdl4fi4rAj0S10/eGMUk31Aij+cOg29rKvSIihuoiZLMsfzxMQnK 7IugC3Bgp2AeXnzyKMAgslWUWIISoHA= Date: Mon, 28 Dec 2020 23:36:50 +0100 From: Borislav Petkov To: Sean Christopherson , Peter Gonda Cc: 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: <20201228223650.GD20321@zn.tnic> References: <20201217010409.3675060-1-pgonda@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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] instead, to get the port byte only, before shifting it into [31:16]. The (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... Hmmm. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette