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[142.79.211.230]) by smtp.gmail.com with ESMTPSA id 19sm2728380oiy.11.2021.05.17.07.24.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 May 2021 07:24:21 -0700 (PDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: a30cd112-584b-4abd-9a00-caaa86fa6486 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=wP0qVRRFLaqKdNsvIebHqzMAQA0sHv3p78V+XQan4IE=; b=SIIetbEYExbcUM1QfmpytUTa2IVHHxjrX5L6JO2j1xRF6GNf1rzKAyM40K3Hi5hYwf REzXM3GmnmYKtfOC3JTzd+8Q5wzYuan+AmqRuwrgoXOPPqC9S/ccK8CLcBCIZT7ro76q vdQ4N0tLO/zXJP4b5wg1VMck/JcqcLbL+m0YijN1z9Wy4KH1jVjVXeFNlbqjhBuEZpFL clyJPWEn6AwkURWyVxA9BsFa3GCFHCy/9/3s1au+ksMHEydPpvbnXHqdH34qXED252Fr 3ipPzVpKQiT02tYGuDwi4Puho9+BjNndIhyvsV44R5iSoKNE4kJ2qajjZsijf8TctP+u qB3A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=wP0qVRRFLaqKdNsvIebHqzMAQA0sHv3p78V+XQan4IE=; b=isZmC00gTfYyKNMr9kV5oYYzpQN5Fpd72C2uSdSXvdNHLC8Q9XI4nIViE6vxe7pEXU vFLbULKGRTZ56hIaykeaLTAbty6GXHNxqErech54FWfMIZ/CzsdfD2pxMVZHWoUKXASz fLS68pq0K/TwE27FCL6nO0y9jrOGIz/RTy9coKke5acItfCnxzBDIzpmv7Mst8DrhgnA SYhTLsjIn5g3V9UgfkQQLq30AJZPAcRJo8GAYVAwGOOaJsObgAcdyQajl4VPWENoRtoW quVpRfDOWlhkjMXCV+c6YIm/g6wYvO65q+qHpGTEAJdlOoJElhOZKRYtQwXEQtzE7nfJ ZS6w== X-Gm-Message-State: AOAM533wTzMGj6pVEZgVLrWbPanXPrYKgYfrV/5eMOVDGBa8yIum3Sod MvIa9khRwZ0x4MZicbAy7+0= X-Google-Smtp-Source: ABdhPJxdOLV4H8+0nYsjoYe7S0t3PHTaJfdsTy6vFeUExppMn/WtX8UkSoPTI9j9rQzIApvCTHBZWA== X-Received: by 2002:a9d:4e88:: with SMTP id v8mr28025140otk.110.1621261462130; Mon, 17 May 2021 07:24:22 -0700 (PDT) Subject: Re: [PATCH v2 1/4] usb: early: Avoid using DbC if already enabled To: Jan Beulich Cc: Jann Horn , Lee Jones , Chunfeng Yun , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, Greg Kroah-Hartman References: <8ccce25a-e3ca-cb30-f6a3-f9243a85a49b@suse.com> <16400ee4-4406-8b26-10c0-a423b2b1fed0@gmail.com> From: Connor Davis Message-ID: <55325db1-b086-fc81-9117-6560c4914a12@gmail.com> Date: Mon, 17 May 2021 08:24:41 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US On 5/17/21 8:13 AM, Jan Beulich wrote: > On 17.05.2021 15:48, Connor Davis wrote: >> On 5/17/21 3:32 AM, Jan Beulich wrote: >>> On 14.05.2021 02:56, Connor Davis wrote: >>>> Check if the debug capability is enabled in early_xdbc_parse_parameter, >>>> and if it is, return with an error. This avoids collisions with whatever >>>> enabled the DbC prior to linux starting. >>> Doesn't this go too far and prevent use even if firmware (perhaps >>> mistakenly) left it enabled? >> Yes, but how is one supposed to distinguish the broken firmware and >> non-broken >> >> firmware cases? > Well, a first step might be to only check if running virtualized. > And then if your running virtualized, there might be a way to > inquire the hypervisor? Right, but if it was enabled by something other than a hypervisor, or you're not running virtualized, how do you distinguish then? IMO the proper thing to do in any case is to simply not use the DbC in linux. Thanks, Connor