Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   David Edmondson <david.edmondson@oracle.com>
To:     linux-kernel@vger.kernel.org
Cc:     "H. Peter Anvin" <hpa@zytor.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>, x86@kernel.org,
        Joerg Roedel <joro@8bytes.org>, Ingo Molnar <mingo@redhat.com>,
        kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
        Jim Mattson <jmattson@google.com>,
        Borislav Petkov <bp@alien8.de>,
        Sean Christopherson <seanjc@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Wanpeng Li <wanpengli@tencent.com>,
        David Matlack <dmatlack@google.com>,
        David Edmondson <david.edmondson@oracle.com>
Subject: [PATCH v6 1/4] KVM: x86: Clarify the kvm_run.emulation_failure structure layout
Date:   Mon, 20 Sep 2021 11:37:34 +0100
Message-Id: <20210920103737.2696756-2-david.edmondson@oracle.com>
In-Reply-To: <20210920103737.2696756-1-david.edmondson@oracle.com>
References: <20210920103737.2696756-1-david.edmondson@oracle.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?tva6jbtarSat3Evn5ihXmjSUaZO9fp1RGsBrnoOv0yX2nLmz9ZmQuT6zP06m?=
 =?us-ascii?Q?CowKqmKF+l4oet1B+qW0iteT4LWCofW6ST1Ojezlu6OPleIPnxpuYgfReYON?=
 =?us-ascii?Q?MbaJgz30nct1XngLmCcv4/eST7YteZGdjPpWfCMAT7eKyUOeYpNsW3+EpY6i?=
 =?us-ascii?Q?QLbfXfahkOBFyvjd1/t4mq6jytGH7XFB8h41fy1hGY/FUnKZ8xsXP2raNHNv?=
 =?us-ascii?Q?L+bQy5q27Eci7LITBar2j8ZITaC8teFDVUDYD7F0AmOi+9A3UV4fCLvhR77t?=
 =?us-ascii?Q?D/mg4aM0X479BQrvGWIjUPSm73lhbVPPCz4xha5+cToS8R8bEQ5vWtVd3cYI?=
 =?us-ascii?Q?jXbtP9379JodwL7Dg2Y4vnkkl3RYIPtWHy7R78FozVCVaviuZhCttVIPF8ZA?=
 =?us-ascii?Q?+VAxbAgU7o68NtlJVE+IMB0bKFZql4oBo0lvmD8AarNMlTgHI05oXxvttHg0?=
 =?us-ascii?Q?Jp0C8+GKy/E9GVpIbOSmOZ8h/Jcb5xX3PTsAdAzqR+NzDnIEEglqEm1GSXxN?=
 =?us-ascii?Q?3cHUDQ3wvBCYcW24NoyZHWIVnPAcIyTaIocuq0g6TIRMRd8e3Y8LJ3ljeptU?=
 =?us-ascii?Q?L+tVAK6M0q3XHxjEItFRXTP5YKxVEROAQ/3WiyXXFZT/MOEPjjlHnSOEl/xj?=
 =?us-ascii?Q?8vyXIbgOk1so/i1277kTGoWra9wKIUzlrE25lU27v1p1vgn9IBanNd8GHvky?=
 =?us-ascii?Q?WtKPQhZGYI+yv2EebJ9mDB0MaV1X9g5DzGvvTFWpis3eARNaf7lnnKaI7ZJ/?=
 =?us-ascii?Q?mNnBUj0nVxwkKUVXy0yBrlvhbt/+cZvr/QAgslmaaYjPYN7YSvz6mVfhrnot?=
 =?us-ascii?Q?Uvm/iLItT1tj4wGmdqnIOeG45z0r6QLfJmvAls0VL1QndrRjgUtNJ5mS6chs?=
 =?us-ascii?Q?ZSHGUKc5Yv49tYIeFKMu1o/59dSx1hYUL2o+SJw9UEdvwt4VKlmmwwsDA6cI?=
 =?us-ascii?Q?iAL7wCnuT32sUboz4CNmgBvZtDKAm4aIJten3/0/K5eUFCH0+yVqedJ8b3/b?=
 =?us-ascii?Q?vXQtuylcJ0Saaz5jC6izR+su2S+ImFiMYj74aUUfFhv3U8vCndmbE13D9Xve?=
 =?us-ascii?Q?FF9dorUGCCkpe1ruRvqCeSEaxPKUAcu1CxYvo4FIA1T8wLIIyQMsjxxpfA3n?=
 =?us-ascii?Q?BOliS9YMJSVM2v2rSunEYYZbnJrUyxKmfz1+GWgjDbmwPAs/RzGCjgn0HPGK?=
 =?us-ascii?Q?38uaU/4jdrBgAs38ZVT51lKBDIJ362i7rrZ0HTCH3nxppodedFbT+P37X19O?=
 =?us-ascii?Q?bgCoISeMNkIi28iUdzcldN189T75RXJ1A2HUdBqmV13zHGd+gJAKkmmgx34J?=
 =?us-ascii?Q?QWFUZ7eJ35oF/K5YriJLI/r0tDdtcY/kxexzKoASPS2JaQ=3D=3D?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: b5d3e4e4-cfa3-4365-f528-08d97c22ae9d
X-MS-Exchange-CrossTenant-AuthSource: DM6PR10MB3148.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Sep 2021 10:37:45.1594
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: r2ZOTKtonmGbopFPtTqXyLDcKnVabA60NhXDHImiH6tCLPNuHkcshrp1z3Lkh/MLcBp3CBGmOeShQiW+5j0WzR1RXsZQWy+LUIbR9FowLUs=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR10MB3308
X-Proofpoint-Virus-Version: vendor=nai engine=6300 definitions=10112 signatures=668682
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 suspectscore=0 spamscore=0
 bulkscore=0 adultscore=0 mlxlogscore=999 malwarescore=0 phishscore=0
 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109030001
 definitions=main-2109200064
X-Proofpoint-GUID: 6M_vuqAIzk5wv0EaPZ9JDKpI8lco8zS9
X-Proofpoint-ORIG-GUID: 6M_vuqAIzk5wv0EaPZ9JDKpI8lco8zS9
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Until more flags for kvm_run.emulation_failure flags are defined, it
is undetermined whether new payload elements corresponding to those
flags will be additive or alternative. As a hint to userspace that an
alternative is possible, wrap the current payload elements in a union.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Edmondson <david.edmondson@oracle.com>
---
 include/uapi/linux/kvm.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index a067410ebea5..8618fe973215 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -402,8 +402,12 @@ struct kvm_run {
 			__u32 suberror;
 			__u32 ndata;
 			__u64 flags;
-			__u8  insn_size;
-			__u8  insn_bytes[15];
+			union {
+				struct {
+					__u8  insn_size;
+					__u8  insn_bytes[15];
+				};
+			};
 		} emulation_failure;
 		/* KVM_EXIT_OSI */
 		struct {
-- 
2.33.0