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b=KpcDe7OfzAUVRoY7d7GU+Blwn8DkIQrc3me+JNgpl0rqRCQWWwxxiPpm6kW6cFBTW5t/g1Pam8LC9sDUkOcbOQ7EAoYDY1qY0cVGocqyYyloZF2W1jWSIsCsA1p34KjcQkO++w4MuVsySLuUqgqj9e+siAEhAiu3kDLLGSBE6hI= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com; Date: Tue, 2 Jun 2026 10:34:16 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: dmukhin@ford.com Cc: xen-devel@lists.xenproject.org, andrew.cooper3@citrix.com, anthony.perard@vates.tech, jbeulich@suse.com, julien@xen.org, michal.orzel@amd.com, sstabellini@kernel.org, Jason Andryuk Subject: Re: [PATCH v6 1/4] xen/console: make console buffer size configurable Message-ID: References: <20260509005714.892018-1-dmukhin@ford.com> <20260509005714.892018-2-dmukhin@ford.com> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260509005714.892018-2-dmukhin@ford.com> X-ClientProxiedBy: BN0PR08CA0007.namprd08.prod.outlook.com (2603:10b6:408:142::32) To CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH7PR03MB7860:EE_|IA1PR03MB8311:EE_ X-MS-Office365-Filtering-Correlation-Id: 238fdcac-bcb1-44cc-bf34-08dec081bd34 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|366016|22082099003|18002099003|56012099006|4143699003|11063799006|3023799007; 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Hm, since you are adjusting the text of the option anyway, the above is not fully accurate. The size of the console ring buffer will be the maximum between the built-time value and the command line option. > > +The default console ring buffer size is selected at build time via > +CONFIG_CONRING_SHIFT setting. > + > ### console > > `= List of [ vga | com1[H,L] | com2[H,L] | pv | dbgp | ehci | xhci | none ]` > > diff --git a/xen/drivers/char/Kconfig b/xen/drivers/char/Kconfig > index 8e49a52c735b..11f48415c12a 100644 > --- a/xen/drivers/char/Kconfig > +++ b/xen/drivers/char/Kconfig > @@ -95,6 +95,21 @@ config SERIAL_TX_BUFSIZE > > Default value is 32768 (32KiB). > > +config CONRING_SHIFT The option just above specifies the size in bytes, and then the code rounds down to the nearest power of 2, but I don't think we can't do the same here, due to how SERIAL_TX_BUFSIZE is used to size an array. > + int "Console ring buffer size (power of 2)" > + range 14 27 > + default 15 > + help > + Select the boot console ring buffer size as a power of 2. > + Run-time console ring buffer size is the same as the boot console ring > + buffer size, unless overridden via 'conring_size=' boot parameter. I don't think the above text is accurate, if `conring_size=` is not specified on the command line the runtime console buffer size will be the maximum between the build time value and `num_present_cpus() << (9 + xenlog_lower_thresh)`. See console_init_postirq(). Thanks, Roger.