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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4E38FC32796 for ; Wed, 24 Aug 2022 18:02:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240528AbiHXSCq (ORCPT ); Wed, 24 Aug 2022 14:02:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42304 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240304AbiHXSCW (ORCPT ); Wed, 24 Aug 2022 14:02:22 -0400 Received: from mail-yw1-x112a.google.com (mail-yw1-x112a.google.com [IPv6:2607:f8b0:4864:20::112a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D01A813CCD for ; Wed, 24 Aug 2022 11:01:28 -0700 (PDT) Received: by mail-yw1-x112a.google.com with SMTP id 00721157ae682-3378303138bso440845637b3.9 for ; Wed, 24 Aug 2022 11:01:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc; bh=DGuV+oKzfmFfApe8NxA2paN6tKmjViwBVg9JpKKUVew=; b=aK7CLkv5P2RcCIQ4lBOyr8TSYIWgo/S7IAXUY+CksZwIzy0GAUD2JwRUYl1mFSlNy1 AlZYZ+MSnfLOvbuZkVTyk5hYpkNwyfw7XjHdVZIEBzoniE+PdMWI3Dkur8HhBI1VH++3 zG2zC0bKMzKEiqxXi/wzfVrA6uOVxHU694jVkzxalWH/7oz6JhUVaNQgLaUVbsF4Ja+t m3unpH32vONLlCtLiTtPrym5TcCuV3jdyoTEvGYk3Tv3xyUaF9kJPtsQZ62M2XcawYY2 /Xq7h71eB0GYT/81B4VArgq0LRAgwploebcVMZfOKDuGJ6M4fYqAWEeqcb1m1QMMjszm Wn2g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc; bh=DGuV+oKzfmFfApe8NxA2paN6tKmjViwBVg9JpKKUVew=; b=C4dnNQwAjN0H/oNLfSwS1xI2ObpSWNLp56bUDfgMyzmDTCAvdr76BBnpsbD5x58wC9 D2qb92pf/N1ShQHqoT/jSAjbkUHe2LRyNulcm8qVOZ54LbSH5PKFfzEMSJ/alXQ590C6 OyJGk3qZHnPEEu4VufXl+lbtDiFvM4+r1j5//+wqq/2dE/hemPfh98hi8Q4mU4jDi5Rh fYKPB11p6VhND1K9QSdPdTA2hSSvb53WyVeKI+mbCFdOeFA2asid0Ug9RWSASW3bT/4C MJ3x3npl1l2VfcDZxkQpqdHcab2GyTzaVGKH75ECXXuoQfcGHV4hiYadIMyyZOGpiEdw r2bQ== X-Gm-Message-State: ACgBeo0jD0rwdACipWgSqvmtqn9PMPxzLeuVY0JAATpbV0tX/eYoL5oG Eo7CZAkdejgGMh7V2K7NbWMUr1/v6PzUyrJTPAe4uA== X-Google-Smtp-Source: AA6agR4krDxQhq5Y+22wT3eQhzuO1h8jJucGBjy3TIVyLauaMRohf/vMydVZsogFXj4WyTvzKkerLZ1BkZP/rZzLJXI= X-Received: by 2002:a81:6f43:0:b0:335:9e7e:ad25 with SMTP id k64-20020a816f43000000b003359e7ead25mr347464ywc.518.1661364087931; Wed, 24 Aug 2022 11:01:27 -0700 (PDT) MIME-Version: 1.0 References: <20220307213356.2797205-1-brijesh.singh@amd.com> <20220307213356.2797205-44-brijesh.singh@amd.com> In-Reply-To: <20220307213356.2797205-44-brijesh.singh@amd.com> From: Dionna Amalie Glaze Date: Wed, 24 Aug 2022 11:01:16 -0700 Message-ID: Subject: Re: [PATCH v12 43/46] virt: Add SEV-SNP guest driver To: Brijesh Singh Cc: "the arch/x86 maintainers" , LKML , "open list:X86 KVM CPUs" , linux-efi , platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev, Linux Memory Management List , Thomas Gleixner , Ingo Molnar , Joerg Roedel , Tom Lendacky , "H. Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Gonda , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Borislav Petkov , Michael Roth , Vlastimil Babka , "Kirill A . Shutemov" , Andi Kleen , "Dr . David Alan Gilbert" , brijesh.ksingh@gmail.com, tony.luck@intel.com, Marc Orr , Kuppuswamy Sathyanarayanan Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Apologies for the necropost, but I noticed strange behavior testing my own Golang-based wrapper around the /dev/sev-guest driver. > + > +static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver, > + u8 type, void *req_buf, size_t req_sz, void *resp_buf, > + u32 resp_sz, __u64 *fw_err) > +{ > + unsigned long err; > + u64 seqno; > + int rc; > + > + /* Get message sequence and verify that its a non-zero */ > + seqno = snp_get_msg_seqno(snp_dev); > + if (!seqno) > + return -EIO; > + > + memset(snp_dev->response, 0, sizeof(struct snp_guest_msg)); > + > + /* Encrypt the userspace provided payload */ > + rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz); > + if (rc) > + return rc; > + > + /* Call firmware to process the request */ > + rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err); > + if (fw_err) > + *fw_err = err; > + > + if (rc) > + return rc; > + The fw_err is written back regardless of rc, so since err is uninitialized, you can end up with garbage written back. I've worked around this by only caring about fw_err when the result is -EIO, but thought that I should bring this up. -- -Dionna Glaze, PhD (she/her)