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Message-ID: Date: Fri, 5 Aug 2022 12:49:40 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH] x86/spec-ctrl: Use IST RSB protection for !SVM systems Content-Language: en-US To: Andrew Cooper Cc: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Wei Liu , Xen-devel References: <20220805103814.23032-1-andrew.cooper3@citrix.com> From: Jan Beulich In-Reply-To: <20220805103814.23032-1-andrew.cooper3@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AM5PR1001CA0001.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:206:2::14) To VE1PR04MB6560.eurprd04.prod.outlook.com (2603:10a6:803:122::25) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 8c79c448-83d1-43a1-d2ca-08da76d0345f X-MS-TrafficTypeDiagnostic: PAXPR04MB9005:EE_ X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:VE1PR04MB6560.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230016)(366004)(376002)(346002)(396003)(39860400002)(136003)(53546011)(26005)(6506007)(186003)(2906002)(6512007)(2616005)(38100700002)(8936002)(8676002)(5660300002)(4326008)(4744005)(66556008)(66946007)(66476007)(6486002)(41300700001)(31686004)(478600001)(86362001)(54906003)(6916009)(316002)(31696002)(36756003)(45980500001)(43740500002);DIR:OUT;SFP:1101; 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Xen does not architecturally execute more > RET than CALL instructions, so an attacker would have to locate a different > gadget (e.g. SpectreRSB) first to execute a transient path of excess RET > instructions. > > Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich