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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0FACC3F6B0 for ; Wed, 24 Aug 2022 18:01:30 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 884C96B0072; Wed, 24 Aug 2022 14:01:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8339A6B0073; Wed, 24 Aug 2022 14:01:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 72315940007; Wed, 24 Aug 2022 14:01:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 6183C6B0072 for ; Wed, 24 Aug 2022 14:01:30 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 310B44037D for ; Wed, 24 Aug 2022 18:01:30 +0000 (UTC) X-FDA: 79835253540.19.DB6926E Received: from mail-yw1-f180.google.com (mail-yw1-f180.google.com [209.85.128.180]) by imf16.hostedemail.com (Postfix) with ESMTP id E06EB18002A for ; Wed, 24 Aug 2022 18:01:28 +0000 (UTC) Received: by mail-yw1-f180.google.com with SMTP id 00721157ae682-335624d1e26so481526697b3.4 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=kQ03Z4Hpnyx8lXFjBgBq5wTYE3RqRDIVvQZYo07fMBxTOrtPv7UNTrA5iScZ8V1fr1 bNCPIacAfKbkisC89AMhqe+WWsTc7c6N9LEyN5lSM3U+mmCO8iOathQ88I9grkos+wCp piueTHSrWbw32CQ8sq0uOAuKXmNEOuBUpcyIxepoEHvkCa5fLrk9/K2aLULIHU6X5igy exIAEfTw2Nc3pKbYoRV3Fiph7fapvVe3CbYW76yMsLWvwoKvUIUOUfCQZr1qZ0lYAQxD U1nd+5GfFJXhrunMfHYIr/O6hXW6G9burfo0nPjtClwfFfGeT+Cg36R0G7vao0s2T0uB hJUg== X-Gm-Message-State: ACgBeo158MLHn25/yI7DrxpdYdiOVUCa1Let4pPA6RRjRiOl+jg5qlpz 66bvjVfO6sMNOZL86cfHHfDA6TN/nix5c7fs/0OMVQ== 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" ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661364088; a=rsa-sha256; cv=none; b=3KnIuVWvLZevQJn88sd7LYsFMw1F2jglS5NKjd3GZKng5syvbDKIuU6jO7BLb0LbcbqeiB dy3tUrKSmXdjC/tAfIoX09oFdmhyZtwDOoWwPDoZpxPjhjqj7IhmQlKltXvf3ngadtcS3o FVyg+rc6v0iLO+No1lBEJkS+ZhypcIk= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=aK7CLkv5; spf=pass (imf16.hostedemail.com: domain of dionnaglaze@google.com designates 209.85.128.180 as permitted sender) smtp.mailfrom=dionnaglaze@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661364088; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=DGuV+oKzfmFfApe8NxA2paN6tKmjViwBVg9JpKKUVew=; b=PU/hvkw5PcwA++im6QOUB9Yt38JthG8atoSsAjULt0/kWZjdPgIEit1U0uggq2u0v86WTM vDj0E2S+aY+gLsDHDTKoAopTEzV1AwzaxT5PFaEhQlfYonJKiPWjp+AGz42BcB0b73jrq3 ZLROUey2joHrMqY0SqjFIUXNfa5lPao= X-Rspam-User: X-Stat-Signature: s7n4jmx94oxakq1kqcmp1841zkt97zfi X-Rspamd-Queue-Id: E06EB18002A X-Rspamd-Server: rspam12 Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=aK7CLkv5; spf=pass (imf16.hostedemail.com: domain of dionnaglaze@google.com designates 209.85.128.180 as permitted sender) smtp.mailfrom=dionnaglaze@google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1661364088-728327 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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)